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MOSSES AND FERNS

THE

STRUCTURE & DEVELOPMENT

OF THE

MOSSES & FERNS

{ARCHEGONIA T^)

■ BY

DOUGLAS HOUGHTON CAMPBELL, Ph.D.

PROFESSOR OP BOTANY
IN THE LBLAND STANFORD JUNIOR UNIVERSITY

l-onlion
MACMILLAN AND CO.

AND NEW YORK

i89S

A a right* reserved

29Mr'99

PREFACE

Ever since the appearance of Hofmeister*s remarkable investi-
gations upon the Archegoniatae, the ever-increasing list of works
upon these plants has borne witness to the interest felt by
botanists in their structure and development. From time to
time the results of these investigations have been collected, but
for the most part this has been done in general text-books,
where want of space has naturally made it impossible, often,
to give much more than a mere summary of results.

The last ten years have been especially noteworthy, not
only for the number of investigations upon the Archegoniates,
but for the extension of our knowledge to many forms which
were hitherto but very imperfectly known. These results have
come from two sources : first, the extension of the field of
research to the Tropics, through the establishment there of
experiment -stations and properly equipped laboratories in
connection with botanical gardens ; second, the advances in
histological methods, especially the use of the microtome in
embryological studies, which have made possible the accurate
determination of many important structural details hitherto but
very unsatisfactorily made out. The application of these more
exact methods of research have made necessary, also, a careful
review of the results of earlier investigations, and the correction
of mistakes due to imperfect manipulations.

The results of these later researches have only begun to
find their way into the text-books, and the present work was
undertaken mainly for the purpose of presenting, in somewhat
detailed form, a r^sum^ of the substance of the great mass of
literature upon the subject which has accumulated, and much of

MOSSES AND FERNS

which is necessarily out of reach of the many botanical workers
who have not access to the great libraries.

Various papers, published by the author from time to time,
have served as the basis of the work, and these have been
supplemented by a somewhat extended series of observations
upon representatives of most of the groups of the Archegoniates,
the results of which are now published for the first time. It
is hoped that the result is a fairly comprehensive statement of
our present knowledge of the comparative morphology of the
Muscineae and Pteridophyta.

Except where otherwise stated, the drawings were made by
the author from his own preparations, and the majority were
prepared expressly for this work.

In view of the extremely unsettled state of botanical
nomenclature at the present time, it was thought best to adopt
a somewhat conservative attitude, and for the most part the
names employed in the text are those which have long been
familiar to the botanical student. Various departures from the
generally accepted arrangement of the orders and families have
been made, the reasons for which are set fprth at sufficient
length in the text.

The author wishes to express his thanks to the many
botanists both at home and abroad to whom he is indebted for
assistance, both in the form of materials and information, with-
out which the work would have been impossible. Especial
thanks are due Professor W. Carruthers, through whose courtesy
the great botanical collections and libraries of the British
Museum at South Kensington were placed at his disposal.
He is also under great obligation to Professor F. O. Bower for
the advance sheets of recent important papers, which made it
possible to complete the latter chapters much more satisfactorily
than otherwise could have been done.

DOUGLAS HOUGHTON CAMPBELL.

Stanford University, California,
March 1895.

CONTENTS

CHAPTER I

PAGE

Introduction ....... i

CHAPTER II

^ MUSCINEiE (BRYOPHYTA)— HEPATICi*: — MARCHANTIACEiE . S

CHAPTER III

MARCHANTIEiE . . 42

CHAPTER IV
The JuNGERMANNiACEif: . . . .71

CHAPTER V
The ANTHOCEROTEiE . . .114

CHAPTER VI
The Mosses (Musci): Sphagnace^ — ANDRE^EACEiE . . '152

CHAPTER VII
The Bryine/E . . . . .180

MOSSES AND FERNS

CHAPTER VIII

PACK

The Pteridophyta — Ophioglossace^e . . . .218

CHAPTER IX

MARATTIACEiE — ISOETACEiE . . . . . .254

CHAPTER X

FiLICINEiE LEPTOSPORANGIATiE ..... 302

CHAPTER XI
Classification of the Homosporous LEPTOSPORANGiATiE . 338

CHAPTER XII

LEPTOSPORANGIATiE HETEROSPOREiE (HYDROPTERIDES) . . 378

CHAPTER XIII

EQUISETINEiE . . . .422

CHAPTER XIV

LVCOPODINEiE . . . . .461

CHAPTER XV

Summary and Conclusions ..... 508

BIBLIOGRAPHY . . '^ . -521

INDEX ........ 535

CHAPTER I

INTRODUCTION

Under the name Archegoniatae are included a large number
of plants which, while differing a good deal in many structural
details, still agree so closely in their essential points of
structure and development as to leave no room for doubting
their close relationship. Besides the Bryophytes and Pteri-
dophytes, which are ordinarily included under this head, the
Gymnospermae or Archespermae might very properly be also
embraced here, but we shall use the term in its more restricted
meaning.

The term Archegoniatae has been applied to these plants
because the female reproductive organ or archegonium is
closely alike, both in origin and structure, in all of them. This^.
is a multicellular body, commonly flask -shaped, and either
entirely free or more or less coherent with the tissues of tHS
plant. In all cases there is an axial row of cells developed, of
which the lowest forms the egg. The others become more or
less completely disorganised and are discharged from the
archegonium at maturity. Among the Algae there is no form
at present known in which the female organ can be certainly
compared to the archegonium, although the oogonium of the
Characeae recalls it in some respects.

The antheridium or male organ of the Archegoniatae,
while it shows a good deal of similarity in all of them, still
exhibits much more variation than does the archegonium, and
is more easily comparable with the same organ in the Algae,
especially the Characeae. Like the archegonium it may be

MOSSES AND FERNS

entirely free, or even raised on a long pedicel ; or it may be
completely sunk in the tissue of the plant, or even be formed
endogenously. It usually consists of a single outer layer of
cells containing chlorophyll, and these enclose a mass of small
colourless cells, the sperm cells, each of which gives rise to
a single ciliated spermatozoid. The development of the latter
is very uniform thr(^ughout the Archegoniatae, and differs
mainly from the same process in the higher green Algae,
especially the Characeae, in the larger amount of nuclear
substance in the spermatozoids of the former.

Fertilisation is only effected when the plants with ripe
sexual organs are covered with water. The absorption of
water by the mature sexual organs causes them to open, and
then, as the spermatozoids are set free, they make their way
through^ the water by means of their cilia and enter the open
archegonium, into which they penetrate to the egg. The
sexual cells do not differ essentially from those of the higher
Algae, and point unmistakably to the origin of the Arche-
goniatae from similar aquatic forms. Indeed all of the
Archegoniatae must still be considered amphibious, inasmuch
as the gametophyte or sexual plant is only functional when
partially or completely submerged.

Non-sexual gonidia are known certainly only in Aneura^
one of the lower Liverworts, but special reproductive buds or
gemmae, both unicellular and multicellular, are common in
many forms.

A v6ry marked characteristic of the whole group is the
sharply-marked alternation of sexual and non-sexual stages.
The sexual plant or gametophyte varies much in size and
complexity. It may be a simple flat thallus comparable in
structure to some Algae, and not superior to these in com-
plexity so far as the vegetative parts are concerned. In others
it becomes larger and shows a high degree of differentiation.
Thus among the Liverworts the Marchantiaceae, while the
gametophyte still retains a distinctly thalloid form, still show
a good deal of variety in the tissues of which the thallus is
composed. In others, e,g. the true Mosses, the gametophyte
has a distinct axis and leaves, and in the higher ones the
tissues are well differentiated for special functions. The
gametophyte itself may show two well-marked phases, the
protonema and the gametophore. The former is usually

INTRODUCTION

filamentous, and arises directly from the germinating spore ;
and upon the protonema, as a special branch or bud, the much
more complex gametophore is borne. Often, however, as in
many thallose Liverworts and Pteridophytes, the protonema is
not clearly distinguishable from the gametophore, or may be
completely suppressed. In the Pteridophytes the gametophyte
is, as a rule, much simpler than in the Bryophytes, resembling
most nearly the less specialised forms of the latter. In the so-
called heterosporous Pteridophytes the gametophyte becomes
extremely reduced and the vegetative part almost entirely
suppressed, and its whole cycle of development inay, in
extreme cases, be completed within twenty-four hours or even
less.

The non-sexual generation, or " sporophyte," arises normally
from the fertilised egg, but may in exceptional cases develop as
a bud from the gametophyte. In its simplest form all the
cells of the sporophyte, except a single layer upon the out-
side, give rise to spores, but in all the others there is developed
a certain amount of vegetative tissue as well, and the sporo-
phyte becomes to a limited extent self-supporting. In the
higher Bryophytes the sporophyte sometimes exceeds in size
the gametophyte, and develops an elaborate assimilative system
of tissues, abundantly supplied with chlorophyll and having an
epidermis with perfect stomata ; but even the most complex
moss-sporogonium is to a certain extent dependent upon the .
gametophyte, with which it remains in close connection by
means of a special absorbent organ, the foot In these highly
developed sporogonia the sporogenous tissue occupies but a
small space, by far the greater part of the tissue being purely
vegetative.

In the Pteridophytes a great advance is made in the
sporophyte beyond the most complex forms found among the
Bryophytes. This advance is twofold, and consists both in an
external differentiation and a more perfect development of the
tissues. The earliest divisions of the embryo resemble very
closely those of the Bryophyte sporogonium, but at an early
stage four distinct organs are usually plainly distinguishable,
viz. stem, leaf, root, and foot. The last corresponds in some
degree to the same organ in the moss-sporogonium, and like it
serves as an absorbent organ by which the young sporophyte
is supplied with nourishment from the gametophyte. In short.

MOSSES AND FERNS

the young sporophyte of the Pteridophyte, like that of the
Bryophyte, lives for a time parasitically upon the gametophyte.
Sooner or later, however, the sporophyte becomes entirely
independent. This is effected by the further growth of the
primary root, which brings the young sporophyte into direct
communication with the earth. The primary leaf, or
cotyledon, enlarges and becomes functional, and new ones
arise from the stem apex. Usually by the time this stage
is reached the gametophyte dies and all trace of it soon
disappears. In some of the lower forms, however, the game-
tophyte is large and may live for many months, or even years,
when not fecundated, and even when the sporophyte is formed,
the prothallium (gametophyte) does not always die immediately,
but may remain alive for several months. The spore-forming
nature of the sporophyte does not manifest itself for a long time,
sometimes many years, so that spore-formation is much more
subordinate than in the highest Bryophytes. With few excep-
tions the spores are developed from the leaves and in special
organs, sporangia. In the simplest cases, ue. Ophioglossunty
the sporangia are little more than cavities in the tissue of the
sporiferous leaf, and project but little above its surface.
Usually, however, the sporangia are quite free from the leaf
and attached only by a stalk. These sporangia are in the
more specialised forms of very peculiar and characteristic
structure, and are of great importance in classification.

Corresponding to the large size and development of special
organs in the sporophyte of the Pteridophytes, there is a
great advance in the specialisation of the tissues. All of the
forms of tissue found in the Spermaphytes occur also among the
Pteridophytes, which indeed, so far as the character of the
tissues of the sporophyte is concerned, come much nearer to the
former than they do to the Bryophytes. This is especially-
true of the vascular bundles, which in their complete form
are met with first in the sporophyte of the Pteridophyta. In
size, too, the sporophyte far exceeds that of the highest Mosses ;
while in these the sporogonium never exceeds a few centimetres
in extreme height, in some Ferns it assumes tree-like pro-
portions with a massive trunk lo to 15 metres in height,
with leaves 5 to 6 metres in length.

In the formation of the spores all of the Archegoniatae
show great uniformity, and this extends, at least as regards

INTRODUCTION

the pollen spores, to the Spermaphytes as well. In all cases the
spores arise from cells which at first form a solid tissue arising
from the division of a single primary cell, or group of cells
(Archesporium). These cells later become more or less
completely separated, and each one of these so-called " spore
mother cells," by division into four daughter cells, forms the
spores. The young spores are thin walled, but later the wall
becomes thicker and shows a division into two parts, one inner
larger, which generally shows the cellulose reaction and is called
the endospore (intine), and an outer more or less cuticularised
coat, the exospore (exine). In addition a third outer coat
(perinium, epispore) is very generally present As the spore
ripens there is developed within it reserve food materials in
the form of starch, oil, and albuminous matter, and quite
frequently chlorophyll is present in large quantity. Some
spores retain their vitality but a short time, those of most
species of Equisetum and Osmunda^ for example, germinating
with difficulty if kept more than a few days after they are
shed, and very soon losing their power of germination com-
pletely. On the other hand, some species of Marsilia have
spores so tenacious of life that they germinate perfectly after
being kept for several years.

From the germinating spore arises the gametophyte bear-
ing the sexual organs. Both archegonia and antheridia may
be borne upon the same plant, or they may be upon separate
ones. Froni the fertilised egg within the archegonium is
produced the sporophyte or non-sexual generation, and from
the spores which it produces arise the sexual individuals again,
thus completing the cycle of development

On comparing the lower Archegoniates with the higher
ones, it is at once evident that the advance in structure consists
mainly in the very much greater development of the sporophyte.
In the Bryophytes, as a class, the gametophyte is more
important than the sporophyte, the latter being, physiologically,
merely a spore-fruit, which in many forms, ue. Sphagnum^ is of
relatively rare occurrence. The gametophyte in such forms is
perennial, and the same plant may produce a large number of
sporogonia, and at long intervals. The sporophyte in such
forms is small and simple in structure, and its main function
is spore formation, as it has but little power of independent
growth. In the Pteridophytes, on the other hand, the gameto-

MOSSES AND FERNS

phyte (prothallium) rarely produces more than one sporophyte,
and as soon as this, by the formation of a root and leaf,
becomes self-supporting, the gametophyte dies. In short, the
sole function of the latter in most of them is to support the
sporophyte until it can take care of itself.

When the lower Pteridophytes are compared with the more
specialised ones, a similar difference is found. In the lower
forms, like the Marattiaceae and Equisetaceae, the gametophyte
is relatively large and long-lived, and closely resembles certain
Liverworts. In these forms a considerable time elapses before
sexual organs are produced, and in artificial cultures of the
Marattiaceae a year or more sometimes passes before archegonia
are formed. These prothallia, too, multiply by budding, much
as the Liverworts do. In case no archegonia are fecundated
the prothallium may grow until it reaches a length of three or
four centimetres, and resembles in a most striking manner a
thalloid Liverwort. In such large prothallia it is not unusual for
more than one archegonium to be fecundated, although usually
only one of the embryos comes to maturity, and the prothallium
may continue to live for some time after the sporophyte has
become independent. Usually, however, as soon as an arche-
gonium is fertilised, the formation of new ones ceases, and as
soon as the sporophyte is fairly rooted in the ground the
prothallium dies.

In most of the lower Pteridophytes the prothallia are
monoecious, but in the more specialised ones are markedly
dioecious. When this is least marked the males and females
differ inainly in size, the latter being decidedly larger ; in the
more extreme cases the difference is much more pronounced
and is correlated with a great reduction in the vegetative part
of the gametophyte in both males and females. This reaches
its extreme phase in the so-called heterosporous forms. In
these the sex of the gametophyte is already indicated by the
character of the spore. Two sorts of spores are produced, lai^e
and small, which produce respectively females and males. In
all of the heterosporic Pteridophytes the reduction of the
vegetative part of the gametophyte is very great, especially in
the male plants. Here this may be reduced to a single quite
functionless cell, and all the rest of the plant is devoted to the
formation of the single antheridium. In the female plants the
reduction is not so great ; and although sometimes but one

INTRODUCTION

archegonium is formed, there may be in some cases a consider-
able number, and owing to the large amount of nutritive
material in the spore, in case an archegonium is not fertilised,
the prothallium, even if it does not form chlorophyll, may grow
for a long time at the expense of the food materials that
normally are used by the developing embryo. In strong
contrast to the slow growth and late development of the
reproductive organs in the homosporous forms, most of the
heterosporous Pteridophytes germinate very quickly. The
Marsiliaceae, in which the female prothallium is extremely
reduced, show the opposite extreme. Here the whole time
necessary for the germination of the spores and the maturing
of the sexual organs may be less than twenty-four hours, and
within three or four days more the embryo is completely
developed.

That heterospory has arisen independently in several widely
separated groups of Pteridophytes is plain. The few genera
that still exist are readily separable into groups that have
comparatively little in common beyond possessing two sorts of
spores ; but each of these same forms shows much nearer
affinities to certain widely separated homosporous groups.

In some of the heterosporous forms the first divisions in the
germinating spore take place while it is still within the
sporangium, and may begin before the spore is nearly fully
developed. In other cases the sporangia become detached
when ripe, and the spore (or spores), still surrounded by the
sporangium, falls away from the sporophyte before germination
begins. In these respects the heterosporous Pteridophytes
show the closest analogy with the similar processes among the
lower Spermaphytes, where it has been shown in the most
conclusive manner that the ovule with its enclosed embryo-sac
is the exact morphological equivalent of the macrosporangium
of Selaginella or Azolla, for example, and that the seed is
simply a further development of the same structure.

CHAPTER II

MUSCINEiE (BRYOPHYTA) HEPATIC^ — MARCHANTIACE^

The first division of the Archegoniatae, the Muscineae or
Bryophyta, comprises the two classes, Hepaticae or Liverworts,
and the Musci or Mosses. In these as a rule the gametophyte
is much more developed than the sporophyte, and indeed in
many forms the latter is very rarely met with. They are
plants of small size, ranging in size from about a millimetre
in length to 30 centimetres or more. A few of them are
strictly aquatic, ue, Riella and Ricciocarpus among the Hepa-
ticae, and Fontinalis of the Mosses ; but most of them grow
upon a solid substratum. A favourite position for many is
the trunks of trees or rocks. Many others grow upon the
earth. They vegetate only when supplied with abundant
moisture, and some forms are very quickly killed if allowed to
become dry ; but those species which grow in exposed places
may be completely dried up without suffering, and some of
those that inhabit countries where there are long dry periods
may remain in this condition for months without losing their
vitality, reviving immediately and resuming growth as soon as
they are supplied with the requisite moisture.

The germinating spores usually produce a more or less
well-marked " protonema," from which the gametophore arises
secondarily. The protonema sometimes is persistent and forms
a dense conferva-like growth, but more commonly it is tran-
sient and disappears more or less completely after the
gametophore is formed. No absolute line, however, can be
drawn between protonema and gametophore, as the former
may arise secondarily from the latter, or even from the
sporophyte. With very few exceptions, ue, Buxbaumia^ the

CH. II MUSCINEjE— HEPATIC^— MARCH ANTIACE^ 9

gametophyte of the Muscineae is abundantly supplied with
chlorophyll, and therefore capable of entirely independent
growth. No true roots are found, but root-hairs afe generally
present in great numbers, and these serve both to fasten the
plant to the substratum and also to supply it with nutriment

The form of the gametophyte varies much. In the
simplest Hepaticae, like Aneura and Pellia^ it is a flat, usually
dichotomously branched thallus composed of nearly or quite
uniform cells, without traces of leaves or other special organs.
From this simplest type, which is quite like certain Algae,
differentiation seems to have proceeded in two directions ; in
the first instance the plant has retained its thalloid character,
but there has been a specialisation of the tissues, as we see
in the higher Marchantiaceae. In the second case the differ-
entiation has been an external one, the thalloid form giving
place to a distinct leafy axis. This latter form reaches its
completest expression in the higher Mosses, where it is accom-
panied by a high degree of specialisation of the tissues as well.
The growth is usually from a single apical cell, which varies
a good deal in form among the thalloid Hepaticae, but in the
foliose Hepaticae and Mosses is with few exceptions a three-
sided pyramid.

The gametophyte of the Muscineae frequently is capable
of rapid jnultiplication, which may occur in several ways.
Where a filamentous protonema is present this branches ex-
tensively, and large numbers of leafy axes may be produced
as buds from it. Sometimes these buds are arrested in their
development and enter a dormant condition, and only ger-
minate after a period of rest. Another very common method
of multiplication is for the growing ends of the branches of a
plant to become isolated by the dying away of the tissues
behind them, so that each growing tip becomes the apex of a
new plant. Very common in the Hepaticae, but less so in the
Mosses, is the formation of gemmae or special reproductive
buds. These are produced in various ways, the simplest being
the separation of single cells, or small groups of cells, from the
margins of the leaves. In the case of Aneura multifida they
are formed within the cells and discharged in a manner that
seems to be identical with that of the zoospores of many Algae.
Again, multicellular gemmae of peculiar form occur in several
of the Hepaticae, e.g, Blasia, Marchantia, where they occur in

lo MOSSES AND FERNS chap.

special receptacles, and among the Mosses similar ones are
common in Tetraphis and some other genera.

The archegonia of all the Muscineae agree closely in their
earlier stages, but differ more or less in the different groups
at maturity. In all cases the archegonium arises from a single
superficial cell, in which three vertical walls are formed that
intersect so as to form an axial cell and three peripheral ones.
From the axial cell develop the egg, canal cells, and cover cells
of the neck, and from the peripheral cells the wall of the venter
and the outer neck cells. In all Muscineae except the Antho-
ceroteae the archegonium mother cell projects above the sur-
rounding cells, but in the latter the mother cell does not project
at all, and the archegonium remains completely sunken in the
thallus. In all other forms the archegonium is nearly or quite
free, and usually provided with a short pedicel. This is especi-
ally marked in the Mosses, where the lower part of the arche-
gonium is as a rule much more massive than in the Hepaticae.

The most marked difference, however, between the arche-
gonium of the Hepaticae and Mosses is in the history of the
cover cell or uppermost of the axial row of cells of the young
archegonium. This in the former divides at an early period
into four nearly equal cells by vertical walls, the resulting cells
either remaining undivided, or undergoing one or two more
divisions ; but in the Mosses this cell functions as an apical
cell, and to its further growth and division the whole growth
of the neck is due.

The antheridia, except in the Anthoceroteae, also arise from
single superficial cells, and while they differ much in size and
form, are alike in regard to their general structure. The
antheridium always consists of two parts : a stalk or pedicel,
which varies much in length, and the antheridium proper, made
up of a single layer of superficial cells and a central mass of
small sperm cells. The former always contain chloroplasts,
which often become red or yellow at maturity. The sperm
cells have no chlorophyll, but abundant protoplasm artd a large
nucleus, which latter forms the bulk of the body of the sper-
matozoid found in each sperm cell of the ripe antheridium.
The spermatozoids are extremely minute filiform bodies,
thicker behind and provided with two fine cilia attached to
the forward end. Adhering to the thicker posterior end there
may usually be seen a delicate vesicle, which represents the

II MUSCINEjE—HEPA TIC^—MARCHANTIA CEJE 1 1

remains of the cell contents not used up in the formation of
the spermatozoid.

When the ripe sexual organs are placed in water their
outer cells absorb water rapidly and become strongly distended,
while the central cells, i.e, the canal cells of the archegonium,
and the sperm cells, whose walls have become mucilaginous,
have their walls dissolved. The swelling of the mucilage
derived from the walls of the central cells, combined with the
pressure of the strongly distended outer cells, finally results
in the bursting open of both archegonium and antheridium.
In the former, by the forcing out of the remains of the canal
cells an open channel is left down to the egg, which has been
formed by the contracting of the contents of the lowest of the
axial cells. In the antheridium the walls of the sperm cells
are not usually completely dissolved at the time the anther-
idium opens, so that the spermatozoids are still surrounded
by a thin cell wall when they are first discharged. This soon
is completely dissolved, and the spermatozoid then swims
away. The substance discharged by the archegonium exer-
cises a strong attraction upon the spermatozoids, which are
thus directed to the open mouth of the archegonium, which
they enter. Only a single one actually enters the egg, where
it fuses with the egg-nucleus, and thus effects fertilisation. The
egg immediately secretes a cellulose wall about itself, and
shortly after the fusion of the nuclei is complete the first
segmentation of the young embryo takes place.

The origin of the sexual organs is from a single cell, but
the position of this cell varies much. In the thalloid Hepaticae
it is a superficial cell, formed from a segment of the apical cell
either of a main axis or of a special branch. In most of the
foliose Hepaticae and the Mosses, the apical cell of the shoot
becomes itself the mother cell of an archegonium, and of course
with this the further growth of the axis is stopped. The
antheridia in the foliose Hepaticae are usually placed singly
in the axils of more or less modified leaves, but in most Mosses
the antheridia form a terminal group. Mixed with the sexual
organs are usually found sterile hair -like organs, paraphyses,
often of very characteristic forms. In the foliose Hepaticae
and most Mosses, the archegonia are often surrounded by
specially modified leaves, and in the former there is also an
inner cup-like perichaetium formed from the tissue surrounding

12 MOSSES AND FERNS chap.

the archegonia. In the thallose Hepaticae, both antheridia
and archegonia are generally enclosed by a sort of capsule,
similar to the perichaetium of the foliose forms formed by the
growth of the tissue of the thallus immediately surrounding
them.

The Asexual Generation
{Sporophyte^ Sporophore^ Sporogonium)

The sporophyte of the Muscineae is usually known as the
" sporogonium," and, as already stated, never becomes entirely
independent of the gametophyte. After the first divisions are
completed there is at an early period, especially in the
Hepaticae, a separation of the spore-producing tissue or arche-
sporium, all the cells of which may produce spores, as in Riccia
and the Mosses, or a certain number form special sterile cells
which either undergo little change and serve simply as nourish-
ment for the growing Sphcerocarpus^ or more commonly assume
the form of elongated cells, — elaters, which assist in scattering
the ripe spores.

Classification

Class I. Hepaticce {Liverworts)

The protonema is either rudimentary or wanting, and not
sharply differentiated from the gametophore. The game-
tophore is, with the exception of Riella Haplomitrium and
Calobryuniy strongly dorsiventral, and may be either a (usually
dichotomously) branched thallus or a stem with two or three
rows of leaves. Non-sexual multiplication of the gametophyte
by the separation of ordinary branches, or by special reproductive
bodies, gonidia {Aneura multifidd) or gemmae — (many foliose
Jungermanniacece, Blasia, Marchantia, etc.). The sporogonium
(except in Anthoceroteae) remains within the enlarged venter
(Calyptra) of the archegonium until the spores are ripe. Before
the spores are shed the sporogonium generally breaks through
the calyptra by the elongation of the cells of the stalk or seta.
All the cells of the ^rchesporium may produce spores, or part
of them may produce sterile cells or elaters.

MUSCINE^—HEPATIC^^MARCHANTIACEjE 13

Class II. Musd {Mosses)'

The gametophyte shows a sharp separation into protonema
and gametophore. The protonema arises primarily from the
germinating spore, and may be either a flat thallus or more
commonly an extensively branching confervoid growth. Upon
this as a bud the gametophore arises. This has always a more
or less developed axis about which the leaves are arranged
in two, three, or more rows. A bilateral arrangement of the
leaves is rare, and the stems branch monopodially. The
asexual multiplication is by the separation of branches through
the dying away of the older tissues, or less commonly by
special buds or gemmae. Both stem and leaves have the
tissues more highly differentiated than is the case in the
Hepaticae. The archesporium is developed as a rule later
than is the case in the Hepaticae, and within is a large central
mass of tissue, the columella, which persists until the capsule
is ripe. In most case^ there is a large amount of assimilative
tissue in the outer part of' the capsule, and the epidermis at its
base is provided with stomata. The growing embryo breaks
through the calyptra at an early stage, and the upper part is
in most cases carried up on top of the elongating sporogonium.
In very much the greater number of forms the top of the
capsule comes away as a lid (operculum).

The HepaticcB

The Hepaticae show many evidences of being a primitive
group of plants, and for this reason a thorough knowledge of
their structure is of especial importance in studying the origin
of the higher plants, as it seems probable that all of these
are derived from Liverwort-like forms. On comparing the
Hepaticae with the Mosses one is at once struck with the very
much greater diversity of structure shown by the former group,
although the number of species is several times greater in the
latter. On the one hand, the Hepaticae approach the Algae,
the thallus of the simpler forms being but little more compli-
cated than that of many of the higher green Algae. On the
other hand, these same simpler Liverworts resemble in a most
striking manner the gametophyte of the Ferns. The same

14 MOSSES AND FERNS chap.

difference is observed in the sporophyte. This in the simplest
Liverworts, e.g, Riccia^ is very much like the spore-fruit of
ColeochcBte, one of the confervoid green Algae ; on the other
hand, the sporogonium of Antkoceros shows some most
significant structural affinities with the lower Pteridophytes.
The simplest form of the gametophyte among the Hepaticae
is found in the thallose Jungermanniaceae and Anthoceroteae.
In such forms as Aneura (Fig. 38) and Antkoceros (Fig. 55)
the thallus is made up of almost perfectly uniform chlorophyll-
bearing tissue, fastened to the earth by means of simple
root -hairs. In forms a little more advanced, ix. Metzgeria^
Pallavicinia (Fig. 38), there is a definite midrib present.
From this stage there has been a divergence in two directions.
In one series, the Marchantiaceae, there has been a specialisa-
tion of the tissues, with a retention of the thalloid form of
the plant. In Riccia (Figs. 1-9) we find two clearly marked
regions, a dorsal green tissue, with numerous air-spaces, and a
ventral compact colourless tissue. In the higher Marchantiaceae
(Fig. 16) this is carried still further,* and the air-chambers
often assume a definite form, and a distinct epidermis with
characteristic pores is formed. In the Marchantiaceae also,
ventral scales or leaf-like lamellae are developed, and root-hairs
of two kinds are present. Starting again from the flat, simple
thallus of Aneura {Riccardia)y two other characteristic types are
met with, the peculiar spiral thallus of Riella^ and the leafy
axis of the more specialised Jungermanniaceae. Between the
latter and the strictly thallose forms are a number of interesting
intermediate forms, like Blasia and Fossombronia^ where the first
indication of the two dorsal rows of leaves is met with ; and
in Blasia at least the rudiments of the ventral row of small
leaves (Amphigastria) usually found in the foliose forms are
present.

The tissues of the Liverworts are very simple, and consist
for the most part of but slightly modified parenchyma.
Occasionally (JPreissia) thickened sclerenchyma - like fibres
occur, but these are not common. Mucilage cells of various
kinds are common. The secreting cells may be hairs on the
ventral surface, and especially developed near the apex, where
the mucilaginous secretion serves to protect against drying up ;
or they may be isolated (Marc/mntia) or rows of cells {Cono-
cepkalus) within the tissue of the thallus. * In the Anthoceroteae

II MUSCINEyE—HEPA TICjE—MARCHANTIA CE^ i 5

stoma-like slits upon the ventral surface lead to cavities where
great quantities of mucilaginous matter are secreted.

The growth of the gametophore is usually due to the
division of a single apical cell. In some of the thallose forms,
e,g. Marchantiaceae, Anthoceroteae, a single initial cell is not
always to be recognised in the older thallus, but in these forms
a single initial always appears to be present in the earlier
stages. In the Jungermanniaceae, however, a single apical cell
is always distinguishable, but varies a good deal in form in
different genera, at least among the thalloid forms, or even in
the same genus. Among the foliose Jungermanniaceae it always
has the form of a three-sided pyramid. From the apical cell
segments are cut off in regular succession, and the first divisions
of the segments also show much regularity, and often bear a
definite relation to the tissues of the older parts.

The Sexual Organs

The archegonium is always traceable to a single cell, but

the position of the mother cell is very different in different

genera. In the simplest cases, eg, Ricda^ Sphcerocarpus (Figs,

2, 29), the mother cell is formed from a superficial cell of one

of the youngest dorsal segments of the apical cell, close to the

growing point of an ordinary branch of the thallus, whose

growth is in no way affected by the formation of archegonia.

rin such forms the archegonia stand alone, and about each is

developed a sort of involucre by the growth of a/ing of cells

immeciiately surrounding the archegonium rudiment.*^ In other

cases the archegonia are found in groups, eg, PaUavicinia (Fig.

38), separated by spaces where no archegonia are found.

Here each group of archegonia has a common involucre. In

Aneura and most of the higher Marchantiaceae the archegonia

• are found in the same way, but upon special modified branches.

In the foliose Jungermanniaceae the origin of the archegonia

is somewhat different. ' Here they are formed upon short

branches, where, after a small number of perichaetial leaves

have been formed, the subsequent segments of the apical cell

develop archegonia at once, and finally the apical cell itself

becomes the mother cell of the last-formed archegonium, and,

of course, with this the growth in length of the branch ceases.

With the deception of the Anthoceroteae, where the archc-

i6 MOSSES AND FERNS chap.

gonium mother cell does not project at all, it quickly assumes
a papillate form and is divided by a transverse wall into a
basal cell, and an outer one from which the archegonium
itself develops. The divisions in this outer cell are remarkably-
uniform. Three vertical walls are first formed, intersecting so
as to enclose a central cell (Fig. 2, G). In this central cell a
transverse wall next cuts off a smaller, upper cell (cover cell)
from a lower one. Subsequently the three (or in the
Jungermanniaceae usually but two) first - formed peripheral
cells divide again vertically, and by transverse walls in all
of the peripheral cells, and somewhat later in the central one
also, the young archegonium is divided into two tiers, a lower
one or venter, and an upper one, the neck (Fig. 2, F). The
middle cell of the axial row, by a series of transverse walls,
gives rise to the row of neck canal cells, and the lowermost
cell divides into two an upper one, the ventral canal cell, and
a larger lower one, the egg.

The antheridium shows very much greater diversity in its
structure, and equally great difference in its position. The
origin in the thallose forms is usually the same as that of the
archegonium, and indeed where the two grow mixed together,
as in many species of Ricciay it is sometimes difficult to
distinguish them in their earliest stages. Usually, however,
the antheridia are borne together, either on special branches
{Marchantia^ species of Aneura\ or they are produced in a
special part of the ordinary thallus, which usually presents a
papillate appearance {e.g. Fimbriaria), In the foliose Junger-
manniaceae the antheridia are often borne singly in the axils
of slightly modified leaves, but in no case does the apical cell
of the shoot become transformed into an antheridium. With
the exception of the Anthoceroteae, where the antheridia are of
endogenous origin, the antheridium, like the archegonium, arises
from a single superficial cell. The first division usually divides
the primary cell into a stalk cell and the body of the anther-
idium. The first may remain very short and undergo but
few divisions, or it may develop into a stalk of considerable
length. The first division in the upper cell may be either
transverse (Marchantiaceae, Spfuerocarpus) or vertical (Junger-
manniaceae). Later, by a series of periclinal walls, a central
group of cells is separated from an outer single layer of cells.
The latter divide only a few times, and develop chlorophyll,

11 MUSCINE^— HEPATIC^— MARCHANTIACE^ 17

which sometimes changes into a red or yellow pigment at
maturity. The inner cells give rise to a very large number of
sperm cells, which in most Hepaticae are extremely small, and
consequently not well adapted to studying the development of
the spermatozoids. In a few forms, however, they are larger ;
and in Pellia especially, where the sperm cells are relatively
large, the development has been carefully studied by Guignard,^
Buchtien,^ and others of late years, as well as by many of the
earlier observers, and a comparison with other Hepaticae
shows great uniformity in regard to the origin and development
of the spermatozoid. After the last division of the central cells
the nuclei retain their flattened form, and thus the sperm cells
remain in pairs^ an appearance very_ cpmmon_in_the ripe
antHeridium of most Liverworts. Just before the differentiation
of the body of the spermatozoid begins, the nucleus has the
appearance of an ordinary resting nucleus, but no nucleolus
can be seen. The first change is an indentation in the edge of
the discoid nucleus, and this deepens rapidly until the nucleus
assumes a crescent form. One of the ends is somewhat sharper
and more slender than the other, and this constitutes the
anterior end. As the body of the spermatozoid grows in length
it becomes more and more homogeneous, the separate chromo-
somes apparently fusing together as the body develops. The
body of the spermatozoid increases in length until it forms a
slender spiral band coiled in a single plane, lying parallel with
the one in its sister cell.

The full-grown spermatozoid in Pellia epiphylla has, accord-
ing to Guignard,^ from three to four complete colls. Most
Hepaticae have much smaller spermatozoids, and they have
fewer coils than in Pellia. In all the Hepaticae the spermato-
zoid is provided with two cilia, which sometimes exceed in
length the body. There is still some disagreement as to
their exact method of formation, but from the latest re-
searches of Strasburger* it seems probable that they arise
as direct outgrowths of the forward end of the body of
the spermatozoid, this pointed anterior portion not being
nuclear in nature, but composed of what Strasburger calls
" kinoplasm." They begin to form at an early stage in the
development of the spermatozoid, and reach their full length

* Guignard (1). * Buchtien (i).

' Gnignard (1), p. 67. * Strasburger (8), pt. iv. p. 125.

i8 MOSSES AND FERNS chap.

before the body of the spermatozoid is complete. Usually
when the spermatozoid escapes, it has attached to the coil a
Small vesicle which swells up more or less by the absorption
of water. This vesicle is the remains of the cytoplasm of
the cell, and may, perhaps, contain also some of the central
part of the nucleus. Guignard^ asserts that sonletimes the
cytoplasm is all used up during the growth of the spermatozoid,
and that the free spermatozoid shows no trace of a vesicle.

In the Ricciaceae and in Sp/uerocarpus new archegonia
continue to form even after several have been fertilised, so that
numerous sporogonia develop upon the same branch of the
thallus ; but in most Liverworts the fertilisation of an arche-
gonium checks the further formation of archegonia in the same
group, and only those that are near maturity at the time reach
their full development ; and even if more than one archegonium
of a group is fecundated,^..^s_ a rule but one embryo comes to
maturity. \^^

Unquestionably the lowest type of sporogonium is found
in Riccia (Fig. 6). Here the result of the first divisions in
the embryo is a globular mass of cells, which a little later shows
a single layer of peripheral cells and a central mass of spore
mother cells, all of which produce spores in the usuaLway. yThe
sporogonium remains covered by the venter of the archegcpium
until the spores are ripe, and never projects above the surface
of the thallus. The spores only escape after the thallus (or at
least that part of it containing the sporogonia) dies and sets
them free as it decays. In the genus Sphcerocarpus (Fig. 30),
which may be taken to represent the next stage of development,
we notice two points in which it differs from Riccia. In the
first place there is a basal portion (foot), which is simply an
absorbent organ, and takes no part in the production of spores.
Secondly, only a part of the archesporium develops perfect
spores. A number of the spore mother cells remain undivided,
and serve simply to nourish the growing spores. In the .
majority of the Hepaticae the sporogonium shows, besides the
foot and the capsule, an intermediate portion, the stalk or seta,
which remains short until the spores are ripe, when, by a rapid
elongation of its cells, the capsule is forced through the calyptra
and the spores are discharged outside. In these forms, too,
some of the cells of the archesporium remain undivided, and

^ Guignard (i), p. 66.

II MUSCINE^— HEPATIC^— MARCHANTIACEjE 19

very early are distinguished by their elongated shape from the
young spore mother cells. These elongated cells later develop
upon the inner surface of the cell wall peculiar spiral thickened
bands, which are strongly hygroscopic. These peculiar fusiform
cells, the elaters, are found more or less developed in all the
Hepaticae except the lowest ones. The Anthoceroteae differ
very much from the other Hepaticae in the structure of the
sporogonium, as they do in other respects. Here alone among
Bryophytes the sporogonium may have unlimited growth, the
development continuing as long as the gametophyte remains
alive. While in the lowest genus, Notothylas^ the growth is
limited, and the spores and elaters occupy the greater part of
the sporogonium, in Anthoceros the archesporium consists of
but a single layer of cells surrounding a central cylindrical mass
of tissue, the columella, and is separated from the outside of
the capsule by several layers of cells. The outer tissue is rich
in chlorophyll, and there is a well-developed epidermis with large
stomata differing neither in origin nor structure from those of
vascular plants. The foot is very large, and just above it is
a zone of actively dividing cells which cause the growth in
length of the sporogonium.

The dehiscence of the sporogonium is different in the
different orders. In the Ricciaceae and some Marchantiaceae
the ri pe sporogonium opens irregularly ; in a few cases (species
of Fimbriarid) the top of the capsule comes off as a lid ; in
most Jungermanniaceae the wall of the capsule splits vertically
into four valves, and in the Anthoceroteae the sporogonium
divides into two valves like a bean-pod.

The spores are always of the tetrahedral type, i,&, the nucleus
of the spore mother cell divides twice before there is any
division of the cytoplasm, although this division may be
indicated by ridges projecting into the cell cavity, and partially
dividing it before any nuclear division takes place. The four
nuclei are arranged at equal distances from each other near the
periphery of the mother cell, and then between them are formed
simultaneously cell walls dividing the globular mother cell' into
four equal cells having a nearly tetrahedral form. These
tetrads of spores remain together until nearly full grown, or in
a few cases until they are quite ripe. In the ripe spore two,
sometimes three, distinct coats can be seen, the inner one
(endospore, intine) of unchanged cellulose, the outer one

20 MOSSES AND FERNS chap.

(exospore, exine) strongly cutinised and usually having upon
the outside characteristic thickenings, ridges, folds, spines, etc.
Where these thickenings are formed from the outside they
constitute the third coat (perinium, epispore). The exospore
is especially well developed in species where the spores are
exposed to great heat or dryness, and which do not germinate
at once. In those species that are found in cooler and moister
situations, especially where the spores germinate at once, the
exospore is frequently thin. The nucleus of the ripe spore is
usually small. The cytoplasm is filled with granules, mostly
albuminous in nature, with some starch and generally a great
deal of fatty oil that renders the contents of the fresh spore
very turbid. Some forms, especially the foliose Junger-
manniaceae, have also numerous chloroplasts, but this is lacking
usually in those forms that require a period of rest before
germination. In Pellia and Conocephalus the first divisions ih
the germinating spore take place while the spores are still
within the sporogonium.

The germination of the spores begins usually by the forma-
tion of a long tube (germ-tube, " Keimschlauch " of German
authors), into which pass , the granular contents of the spore.
At the same time there fhay be formed a root-hair growing in
a direction opposite to that of the germinal tube, although quite
as often the formation of the first root-hair does not take place
until a later period. If the spore does not contain chlorophyll
before germination, it is developed at an early stage, before any
cell-divisions occur. Often the formation of a germ-tube is
suppressed and a cell surface or cell mass is formed at once,
and all these forms may occur in the same species. The
germination only takes place when the light is of sufficient
intensity, and the amount of light is a very important factor
in determining the form of the young plant. Thus if the light
is deficient, the germ-tube becomes excessively long and slender,
and divisions may be entirely suppressed. An excess of light
tends to the development at once of a cell surface or cell mass.
In the simpler thalloid forms the first few divisions in the
young plant establish the apical cell, and we cannot properly
speak of the gametophore as arising secondarily from a
protonema ; in other cases, however, the young plant does arise
as an outgrowth or bud from a protonema, which only rarely
has the branching filamentous character of the Moss protonema.

MUSCINE^^HEPA TIC^—MARCHANTIACEM 21

Classification of the HEPATiCiE

The Hepaticae are readily separated into the three following
well-marked groups.

Group I. Marchantiaceae.
Group II. Jungermanniaceae.
Group III. Anthoceroteae.

The following diagnoses are taken, with some modifications,
from Schiffner.^

Gro up L Marchantia cem

Gametophyte always strictly thallose, composed of several
distinct layers of tissue, the uppermost or chlorophyll-bearing
cells usually ^containing large air-spaces. The dorsal epidermis
usually provided with pores, ventral surface with scales arranged
in one or two longitudinal rows. Rhizoids of two kinds, with
smooth walls, and papillate ; sexual organs, except in the lowest
forms, united in groups which are often borne on special stalked
receptacles. The first divisions of the embryo are arranged like
the quadrants of a sphere. Sporogonium either with or without
a stalk, and all the inner cells forming spores, or some of them
producing elaters. No columella present.

Fam, I. Rtcciacece

Chlorophyll-bearing tissue with or without air-chambers,
and, where these are present, they never contain a special
assimilative tissue. Epidermal pores wanting or rudimentary.
Sexual organs immersed in open cavities upon the dorsal
surface. Sporogonium without ,fdot or stalk, and remaining
permanently within the venter of the archegonium. All the
cells of the archesporium producing spores.

' Fam. 2. CorsiniecB

Air-chambers well developed ; epidermis with distinct
pores ; sexual organs in distinct grpups, but the receptacles

1 Schiffner (i), p. 5.

22 MOSSES AND FERNS chap.

always sessile ; sporogonium with a short stalk, prodi^cing
besides the spores sterile cells, which may have the form of
very simple elaters.

Fam. 3. Marchantiece

Air-chambers (with exception of Dumortierd) highly
developed, and the chambers in most cases containing a loose
filamentous assimilative tissue. Pores upon the dorsal surface
always present (except in Dumortiera) and highly developed,
ring-shaped or cylindrical. Sexual organs"^ always in groups,
usually upon special long-stalked receptacles. Sporogonium
stalked and when ripe breaking through the calyptra, opening
by teeth or a circular cleft, more seldom by four or eight valves.
The archesporium develops sterile cells, usually in the form of
elaters, as well as spores.

The Marchantiacecs

The Marchantiaceae constitute a very natural order of plants,
all of whose members agree very closely in their fundamental
structure. The separation of the Ricciaceae as a group co-
ordinate with the Jungermanniaceai and Anthoceroteae is not
warranted, as more recent investigations, especially those of
Leitgeb,^ have shown that the two groups of the Marchantiaceae
and Ricciaceae merge almost insensibly into each other.

They are all of them strictly thallose forms, the thallus being
unusually thick and fleshy, and range in size from a few
millimetres in some of the smaller species of Riccia^ to 10 to 20
centimetres in some of the larger species of Dumortiera and
Conocephalus, In most of them branching is prevailingly
dichotomous, and as this is rapidly repeated, it often causes the
thallus to assume an orbicular outline. Some forms, however,
e^, Targionia (Fig. i, E), fork comparatively seldom, and the
new branches are for the most part lateral. The thallus is
fastened to the substratum by rhizoids, which are unicellular
and usually of two kinds, those with smooth walls and those
with peculiar papillate thickenings or teeth that project inward
(Fig. 11). The cells of the lower layers of tissue are usually
nearly or quite destitute of chloroplasts, which, however, occur

^ Ldtgeb (7), vol. iv.

MUSCINEjE—HEPA tic^—marchantiace^

in large numbers in the so-called chlorophyll-bearing layer, just
below the dorsal epidermis. This chlorophyll -bearing layer

Fig. I.— Marchantiaceae. A, B, Male plants of Fimbriaria CaU/omica (Hampe). A, from above ;
B, from below ; <J, antheridial receptacle ; /, ventral lamellx, X4 ; C, Riccia glauca (L.), x6 :
i/, sporogonia; D, Conocepkalus conicm {JZorA^ X4; £, Targionia hypophylla (L.)i X2 ; 6%
antheridial branch.

contains air-spaces in all forms except some species of
Dumortieray and these spaces are either simple narrow canals,

24 MOSSES AND FERNS chap.

as in Riccia glauca^ or they may be large chambers separated
by a single layer of cells from their neighbours. Such forms
occur In most of the higher Marchantiaceae.

The growth of the thallus is due to the division of a small
group of cells occupying the bottom of the heart-shaped indent-
ation in the forward part of the thallus. Sections parallel to
the surface, cutting through this group, show a row of marginal
cells that appear very much alike, and it is impossible always
to tell certainly whether or not there is a single definite initial
cell. Such a single initial is unquestionably present in the
earlier stages, and it is quite possible that it may persist, but
owing to its small size and its close resemblance to the adjoin-
ing cells, this cannot be positively asserted. In vertical sections
the initial cell (or cells) appears nearly triangular, with the
free outer wall somewhat convex. From this cell two sets of
segments are cut off, the dorsal segments giving rise to the
green tissue, and the lower segments producing the ventral
lamellae and colourless lower layers of cells of the thallus.

The plants multiply asexually either by the older parts of
the thallus dying away and leaving the growing points isolated,
or lateral branches, which are often produced in great numbers
from the lower surface of the midrib, become detached and each
branch forms a separate plant The well-known gemmae of
Marchantia and Lunularia are the most striking examples of
special asexual reproductive bodies.

The sexual organs are always derived from the dorsal
segments of the apical cell, either of the ordinary branches or
of special shoots. The archegonium is of the regular form, and
the antheridium always shows a series of transverse divisions
before any longitudinal walls are formed in it.

While the gametophyte may reach a very considerable
degree of specialisation, the sporophyte is relatively insignificant
even in the higher forms, and has the foot and stalk poorly
developed. While the Marchantiaceae grow for the most part
in moist situations, and some of them, e.g, Marchantia polyvtorpha^
are very quickly killed by drying, some species, eg. Riccia hiria,
a common Califomian species, grows by preference in exposed
rocky places exposed to the full force of the sun. This latter
species as well as several others of the same region, e.g.
Fimbriaria Califomicay Targionia hypophylla^ do not die at the
end of the rainy season, but become completely dried up, in

MUSCINE^^HEPA TIC^—MARCHANTIACE^

which condition they remain dormant until the autumn rains
begin, when they absorb water and begin to grow again at once.
In these cases usually only the ends of the branches remain
alive, so that each growing tip becomes the beginning of a new
plant

The Ricciacece

As a type of the simplest of the Marchantiaceae, we may
take the genus RicciUy represented, according to Schiffner,^ by
107 species, distributed over the whole earth. Most of them
are smay terrestrial plants forming rosettes upon clay soil, or
sometimes on drier and more exposed places. A few species,
e^. R. fiuitanSy are in their sterile condition submersed aquatics,
but only fruit when by the evaporation of the water they come
in contact with the mud at the bottom.

..). Development of the aficfafiSfiBUUl. X525. A, Vertical section througlA
the growing point ; jr, apical cell ; ar, young arch^onium ; //, ventral lamella: ; B-F, successive)
stages in the development of the archegonium, seen in longitudinal section ; G, cross-section 06
I archegonium (diagrammatic).

The dichotomously branched thallus shows a thickened
midrib, which is traversed upon the dorsal surface by a longi-
tudinal furrow which in front becomes very deep. At the
bottom of this furrow, at the apex of the thallus, lies the growing
point. A vertical section through this shows a nearly triangular

^ Schiflfner (i), p. 14.

MOSSES AND FERNS

apical cell which lies much nearer the ventral than the dorsal
surface (Fig. 2, x). From this are cut off successively dorsal
and ventral segments. Each segment next divides into an
inner and an outer cell. From the outer cells of the dorsal
segments the sexual organs arise, and from those of the ventral
segments the overlapping lamellae upon the lower surface of the
thallus, and also the root-hairs. The rapid division of the inner
cells of the segments, especially those of the dorsal ones, causes
the thallus to become rapidly thicker back of the apex.

Fig. 3. — Riccia glauca (L.). Horizontal sections of the growing point. A, B, X525 ; C, X about alio.
C shows the dichotomy of the growing point ; x^ x\ the two new growing points ; L, the lobe
between them ; ar, a young archegonium.

Sections made parallel to the surface of the thallus, and pass-
ing through the growing point (Fig. 3), show that the margin
is occupied by a group of cells that look very much alike.
Sometimes one of these cells is somewhat larger than the others,
but more commonly it is impossible to decide with certainty that
a single initial is present. From a comparison of the two sec-
tions it is at once evident that the initial cells have nearly the
form of the segment of a disc, and that in addition to the
dorsal and ventral segments lateral ones are cut off as well.
In the region just back of the apex the tissue of the thallus is

II MUSCINE^—HEPATICjE—MARCHANTIACE^ 27

compact, but in the older parts a modification is observable
both on the dorsal and ventral surfaces. In the former, a short
distance from the growing point, the superficial cells project
in a papillate manner above the surface. This causes little
depressions or pits to be formed between the adjacent cells
(Fig. 3, C). The subsequent divisions in the papillae are
all transverse, and this transforms each papillate surface cell
into a row of cells which, as it elongates, causes the pits
between it and the adjacent ones to become deep but narrow
air-channels, so that in the older parts of the thallus the^per
portion is composed of closely-set vertical rows of chlorophyll-
bearing cells separated by narrow clefts opening at the surface. >,,
In Ric^a glauca^ as well as other species, the uppermost cell of '
each row often enlarges very much, and with its fellows in the
other rows constitutes the epidermis. According to Leitgeb's
researches this epidermal cell is formed by the first division in
the outer cell of the segment, and either undergoes no further
division, or by dividing once by a transverse wall forms a two-
layered epidermis (i?. Bischoffit). On the ventral side the outer
cells of the segments project in much the same way, but they
remain in close contact laterally with the neighbouring cells, so
that instead of forming isolated rows of cells, transverse plates
or lamellae, occupying the median part of the lower surface of
; the thallus, are formed. These remain but one cell thick, and
gtow very rapidly, and bend up so as to completely protect the
growing point With the rapid widening of the thallus in the
older parts these scales are torn asunder, and the two halves
being forced apart constitute the two rows of ventral scales
found in the older parts. Later these scales dry up and are
often scarcely to be detected except close to the growing point.
In the case of Ricciocarpus natans} instead of a single scale
being formed, each cell of the horizontal row, which ordinarily
gives rise to a single scale, grows out independently, much as do
the dorsal surface cells in the other species, and the result is a
horizontal series of narrow scales, each one corresponding to a
single cell of the original row. These later are displaced by
the subsequent growth of the thallus, and their arrangement in
transverse series can only be seen in the younger parts. The
very rapid increase in length of the dorsal rows of cells as they
recede from the growing point soon causes them to overarch

^ Leitgeb(7), vol. iv. p. 29.

28 MOSSES AND FERNS chap.

the latter, which thus comes to lie in a deep groove ; indeed not
infrequently the end cells of the rows on opposite sides of the
groove actually meet, so that the groove becomes a closed tube.

R, fiuitans ^ and R, aystallina differ in some respects from
the other forms. In these, owing to a greater expansion of the
tissues of the older parts of the thallus, the air-spaces are very
much enlarged. In the former they are almost completely
closed above, as the epidermal cells, by repeated vertical divisions,
keep pace with the growth of the thallus and form a continuous
epidermis, with only a small central pore over each of the large
air-chambers. In R. crystallina^ however, there is no such
secondary growth of the epidermal cells, and in consequence the
cavities are completely open above, so that the surface of the
thallus presents a series of wide depressions separated by thin
lamellae. These two species also show some difference as to
the ventral scales. Those in R. fiuitans are small and do not
become separated into two, and in R, crystallina they are
wanting entirely.

Most of the Ricciaceae multiply by special adventive shoots
that arise from the ventral surface of the midrib. These become
detached and form new individuals. According to Fellner ^ the
rhizoids develop at the apex a young plant in a manner entirely
similar to that by which the young plant arises from the germ-
tube of the germinating spore.

By far the commonest method of branching in most species
of Riccia is a true dichotomy. The first indication of tbi&
process is a widening of the growing point and a corresponding
increase in the number of the marginal cells. The central
cells of the marginal group now begin to grow more vigorously
than the others and to project as a sort of lobe (Fig. 3, C, L),
and this lobe divides the initial cells into two groups lying
on either side of it. As soon as this is accomplished each
new group of initials continues to grow in the same manner as
the original group, and two new growing points are established,
each of which develops a separate branch. The growth of the
middle lobe is limited, and it remains sunk in the fork between
the two new branches.

The thallus is attached to the substratum by root-hairs, of
two kinds. The first are smooth-walled elongated cells, with
colourless contents, the others much like ihose of the higher

^ Leitgeb (7), vol. iv. p. 11. ' Fellner (i).

II MUSCINEjE-^HEPA TIC^—MARCHANTIA CE^ 29

Marchantiaceae. Their walls are undulating, and projecting
inward are numerous more or less developed spike-like protu-
berances. The root-hairs arise from large superficial cells of
the ventral part of the midrib. They are readily distinguished
from the adjacent cells by their much denser contents, even
before they have begun to project.

The arrangement of the tissues of the fully -developed
thallus is best seen in vertical cross-sections. In ^. gluuca and
allied forms four well-marked tissue zones can be readily
recognised in such a section. T^e lowest consists of a few
layers of colourless rather loose parenchyma, from which the
root-hairs arise, and to which the ventral lamellae are attached.
Above this a more compact, but not very clearly limited region,
the midrib. The elongated form of the midrib cells, which
contain abundant starch but no dilo^ophyll, is, of course, not
evident in cross -section. Radiating from the midrib are
closely-set rows of chlorophyll-bearing cells jivith the character-
istic narrow air-spaces between. The median furrow is very
conspicuous in such a section, and extends for about half the
depth of the thallus. Terminating each row of green cells is
the enlarged colourless epidermal cells, often extended into a
beak-like appendage. In some species, e,g. R. hirta^ some of
the surface cells grow out into stout thick -walled pointed
hairs.

The Sexual Organs

In Riccia the sexual organs are formed in acropetal suc-
cession from the younger segments of the initial cells, and
continue to form for a long time, so that all stages may be met
with upon the same thallus. While both aiUhecidia and
archegonia may be found together, in the two species R, glauca
and R, hirta^ mainly studied by myself, I found that as a rule
several of one sort or the other would be formed in succession,
and that not infrequently antheridia were quite wanting from
plants that had borne numerous archegonia. Both arch^onia
and antheridia arise from single superficial cells of the younger
dorsal segments of the initial cells. In their earliest stages
they are much alike, the mother cell of the antheridium being,
however, usually somewhat larger than that of the archegonium.
The cell enlarges and projects as a papilla above the surface,
when it is divided by a transverse wall into an outer cell and

MOSSES AND FERNS

an inner one. The latter divides but a few times and forms
the short stalk; the outer cell, which has dense granular
contents, develops into the archegonium or antheridium as the
case may be. In the former case the divisions follow the
order already indicated for the typical Liverwort archegonium.
In the outer cell, which continues to enlarge rapidly, a nearly
vertical wall is formed (Fig. 2, C), which divides the cell into
two very unequal parts. This wall is curved and strikes the
periphery of the mother cell at about opposite points (Fig. 2,
G, f). A second wall of similar form is next formed in^the
larger cell (G, 2), one end of which intersects the first wall,
and finally a third wall (3) intersecting both of the others is
formed. The young archegonium seen in vertical section at
this stage (Fig. 2, D) shows a large central cell bounded by
two smaller lateral ones ; in cross -section the central one
appears triangular. Each of the four cells of which the
archegonium rudiment is now composed divides into two.
The outer ones each divide by radial walls into equal parts,
and the central one divides into an^pper smaller cell (cover
cell) and a lower larger one (Fig. \ E). The next divisions
are horizontal and divide the young archegonium into two
tiers of^ells. The lower one forms the venter, and the upp6r
one the neck, and next the cover cell divides into four nearly-
equal cells by intersecting vertical walls. The archegonium at
this stage (Fig. 2, F) is somewhat pear-shaped, being smaller
at the bottom ^than at the top, and the basal cell is still
undivided. It now rapidly increases in length by the trans-
verse division and growth of all its cells, and there is at the
same time a marked increase in diameter in the venter, which
finally becomes almost globular (Fig. 4). The axial ceU of
the neck, the neck canal cell, divides, according to Janczewski,^
always into four in R, Bischoffii^ and the same seems to be true
for R. hirta (Fig. 4, A), and probably is the same in other
species. The number of divisions in the outer neck cells is
various, but is most active in the lower part, but in the central
cell of the venter there is always but a single transverse
division which separates the ventral canal cell from the egg.
The four primary cover cells enlarge a good deal as the
archegonium approaches maturity, and divide by radial walls
usually once, so that the complete number is normally eight —

' Janczewski (i).

MUSCINE^—HEPA TICyE—MARCHANTIACE^

Janczewski gives ten in R, Bischoffii, The basal cell finally
divides into a single lower cell which remains undivided, com-
pletely sunk in the thallus, and an upper cell which divides
into a single layer of cells forming part of the venter, and
continuous with the other peripheral cells. The mature
archegonium (Fig. 4) has the form of a long-necked flask with
a much enlarged base. The canal cells are completely indis-
tinguishable, their walls having become absorbed and the

Fig. 4'— a, Archegonium of Riccia hirta (Aust.X showing the ventral canal cell (»), X 525 ;
B, ripe archegonium of R. glauccu, longitudinal section, X 26a

contents run together into a granular mass. The nuclei of
the neck-canal celk are small and not readily recognisable after
the breaking down of the cell walls, but ^om analogy with the
higher forms it is not' likely that they completely disappear in
the ripe archegonium. The cytoplasm of the central cell
contracts to form the naked globular egg. The cytoplasm is
filled with granules, and the nucleus, which is of moderate size,
shows a distinct nucleolus, but very little chromatin. A
special receptive spot was not certainly to be seen.

MOSSES AND FERNS

CHAP.

Almost coincident with the first cell division in the
archegonium rudiment there is a rapid growth of the cells
immediately surrounding it. These grow up as a sort of ring
or ridge about the archegonium, which is thus gradually-
immersed in a cup-shaped cavity, and the growth of the cells
about this keeps pace with the increase in length of the
archegonium, so that even when fully grown only the very
extremity of the neck projects above the level of the thallus.
The whole process is undoubtedly but a modification of the

Fig. 5. — A-F, Development of the antheridium of /f. glanca, seen in Ipngituduwl section ; G, cross-
section of a young antheridium of the same ; H, antheridium of R. hirta ; I, sperm cells of R,
g^lauca. Figs. £, F, X150; I, x6oo, the others X300.

ordinary growth of the dorsal part of the thallus, and the
space about the archegonium is' the direct equivalent of the
ordinary air-spaces.

The first division in the primary antheridial cell is the
same as in the archegonium, but the later divisions differ much
and do not show such absolute uniformity. The first division
wall in the upper cell (Fig. 5, B) is always transverse, and
this is followed by a second similar wall, but the subsequent
divisions show considerable variation even in the same species.
After a varying number of transverse walls have been formed,

II MUSCINE^— HEPATIC^— MARCHANTIACE^ 33

in most c^ses the next divisions, which are formed only in the
middle se'gments, are vertical, and divide the segments into
quadrants ^ of a circle when seen in transverse section.
Occasionally a case is met with where the division walls are
inclined alternately right and left, and the divisions strongly
recall those of the typical Moss antheridium (Fig. 5, D).

The separation of the sperm cells is brought about by a
series of periclinal walls in a number of the middle segments,
by which four central cells in each segment (Fig. 5, G) are

-separated from as many peripheral cells. These central cells
have, as usual in such cases, decidedly denser contents than

<the peripheral ones.

The lower one or two segments and the terminal ones do
not take part in the formation of sperm cells, but simply form
part of the wall of the antheridium. The central cells now
divide with great rapidity, the division walls being formed
nearly at right angles to each other, so that the central part of
the antheridium becomes filled with a very large number of
nearly cubical cells. The divisions are formed with^ such -
regularity that the boundaries of the original central cells
remain very clearly marked until the anthepdium is nearly
mature. The basal cell of the antheridium rudiment in /?. ►
glauca divides once by a horizontal wall (Fig. S, B, D) and
forms the short stalk of ,the antheridium, which, however, is
almost completely sunk in the thallus. Between this stalk,
and the central group of cells there are usually two layers of

■ cells, so that the wall of the antheridium is double at the base,
while it has but a single layer of cells in the other parts. The ,
uppermost cells are often, although not always, extended into
a beak. The spermatozoids do not seem to differ either in their
method of development or structure from those of other Hepaticae,
but their excessively small size makes it extremely difficult to

. follow through the details of their developnvent. When ripe the
wall cells are much compressed, but are always to be distinguished.
Like the archegonia, the antheridia are sunk separately in
deep cavities, which are formed in exactly the same way.
Unlike the archegonia, however, the antheridium does not
nearly reach to the top of the cavity, whose upper walls are in
many species very much extended into a tubular neck, which
projects above the general level of the thallus, arid through
which the spermatozoids are discharged.

MOSSES AND FERNS

The Embryo

After jrtiHsation is effected the egg develops at once a
cell-membrane and enlarges until it completely fills the cavity
of the venter. The first division wall is more or less inclined
to the axis of the archegonium, but approaches usually the
horizontal. The lower of the two cells thus formed divides
first by a wall at right angles to the first formed, but this is
followed in the upper half of the embryo by a similar division,
so that the embryo is divided into nearly equal quadrants. In

Fig. 6.— a, B, Young embryos of R. glauca in longitudinal section, showing the venter of the arche-
gonium, X 260 ; C, transverse section of a similar embryo, X 260 ; D, longitudinal section of the
archegonium and enclosed embryo of R. hirta at a later stage, X 220 ; w, the sterile cells of the
sporogonium.

each of the quadrants a wall meeting both of the others at
right angles next appears (Fig. 6, C, III), and the embryo at
this stage consists of eight nearly equal cells. The next walls
are not exactly alike, but the commonest form is a curved wall
(Fig. 6, C) striking two of the others, usually walls II and III, and
intersecting the surface of the embryo. This wall divides the
octants into two cells, which appear respectively triangular and
quadrilateral in section. By the next division the archesporium
is separated from the wall of the sporogonium. These walls

II MUSCINEjE—HEPATICjE—MARCHANTIACEjE 35

are periclinal, and by them a single layer of outer cells is
separated from the central mass of cells which constitutes the
archesporium (Fig. 6, B, D).

At first the cells of the embryo are much alike, but as it
grows the inner cells increase in size and their contents become
densely granular, while the outer cells grow only in breadth,
and not at all in depth, assuming more and more a tabular
form, and for the most part undergo divisions only in a radial
direction, so that the walls remain but one cell thick in most
places. As the sporogonium increases in diameter the central
cells begin to separate and round off. Their walls become
partially mucilaginous, and in microtome sections stain
strongly with Bismarck-brown or other reagents that stain
mucilaginous membranes. With this disintegration of the
division walls the cells separate more and more until they lie
free within the cavity of the sporogonium. Each of these
spore mother cells is a large gobular cell with thin membrane
and densely granular contents. The nucleus is not so large as
is usually the case in cells of similar character, and, except the
tmcleolus, stains but slightly with the ordinary nuclear stains.
In the fresh state these spore mother cells are absolutely opaque,
owing to the great amount of granular matter, largely drops of
oil, that they contain. In embedding these in paraffine,
however, the oil is dissolved and removed, and microtome
sections show the fine granules of the cytoplasm arranged in a
net-like pattern, the spaces between probably being occupied
by oil in the living cells.

Fig. 7, A shows the nucleus of the mother cell under-
going the first division. The small size of the nuclei, and
the small amount of chromation in them, make the study
of the details of the nuclear division difficult here, and as
there was nothing to indicate any special peculiarities these
were not followed out. After the first nuclear division the
daughter nuclei divide again, after which the four nuclei
arrange themselves at equal distances from each other, the
division walls form simultaneously between them, dividing
the spore mother cell into the four tetrahedral spores. A
section through such a young spore-tetrad is shown in Fig.
7, B, where one of the cells is somewhat shrunken in the
process of embedding. The cell walls at this stage are very
delicate and of unchanged cellulose ; but as they grow older

MOSSES AND FERNS

CHAP.

the wall soon shows a separation into endospore and exospore.
The latter in R, hirta, which was especially studied, is very-
thick, at first yellowish in colour, but deepening until when
ripe it is black. Sections parallel to the surface show in this
species what appear to be regular rounded pits, but vertical
sections of the spore-coat show that this appearance is due to
a peculiar folding of the exospore, which also shows a distinct
striation, the outer layer being much thicker and denser than
the inner oqes. The nucleus of the ripe spore is remarkably

Fig. 7. — Riccia hitta (Aust.). A, Section of a spore mother cell undergoing its first division, X600:
B, section of young spore tetrad, X 300 ; C, section of ripe spore, X joo ; D, surface view of the exo-
spore of a similar stage, X 300.

small, and it is evident that the dense contents of the ripe
spore is largely oil or some similar soluble matter, as in
microtome sections there is very little granular matter visible.

At the same time that the first division wall forms in the
embryo, the outer cells of the venter begin to divide by
periclinal walls, so that the single layer of cells in the wall of
the unfertilised archegonium becomes changed into two, and
the basal portion becomes still thicker ; the neck takes no part
in this later growth. The cells of the venter develop a great
deal of chlorophyll, which is quite absent from the sporogonium
itself, and before the spores are ripe the inner layer of cells of

II MUSCINEAl—HEPATICjE—MARCHANTIACEjE 37

the calyptra (venter) becomes almost entirely absorbed, so that
only traces of these cells are visible when the spores are ripe.
The wall of the sporogonium also disappears almost completely
as the latter matures, but usually in microtome sections traces
of this can be made out in the ripe capsule, although the cells
are very much compressed and partially disorganised. The
contents of these cells, as well as the inner calyptra cells, no
doubt are used up to supply the growing spores with nourish-
ment Thus, when ripe, the spores practically lie free in the
cavity surrounded only by the outer layer of calyptra cells.
The neck of the archegonium persists and is made conspicuous
by the dark brown colour of the inner walls of the cells.

Hitherto the germination of the Ricciaceae was only
known in R. glauca} The account here given is based upon
observations made upon R, hirta — a very common Cali-
fornian species. It fruits in winter and early spring, and
the spores remain dormant during the dry summer months.
If the spores are sown in the autumn they germinate within a
few days by bursting the massive black exospore, through
■which the colourless endospore enclosing the spore contents
projects in the form of a blunt papilla. This rapidly grows
out into a long club-shaped filament (Big. 8, A), much less in
diameter than the spore, and into this the spore contents pass.
These now contain albuminous granules and great numbers
of oil-globules, and among these chlorophyll bodies, which
at first are small and not very numerous. They, however,
increase rapidly in size, and divide also, so that before the first
cell division takes place the chloroplasts are abundant and
cpnspicuous. The formation of the first root-hair does not take
place usually until a number of divisions have been formed in
the young thallus. The first root-hair (Fig. 9, R) arises at
the base of the germinal tube, and is almost free from granular
contents. It, usually at least, is separated by a septum from
the germ-tube. The first wall in the latter is usually transverse,
although in exceptional cases it is oblique (Fig. 8, B), and this
is followed by a second one parallel to the first (Fig. 8, C).
In each of these cells a vertical wall is formed, and then a
second at right angles to this, so that the nearly globular mass
of cells at the end of the germ -tube is composed of eight
nearly equal cells or octants. As these divisions proceed the

» Fellner (i).

MOSSES AND J^ERNS

CHAP.

oil drops which arc so abundant in the undivided j^erm-tube
disappear almost completely, and arc doubtless used up by the
growing cells.

According to Lcitgebs view, and tliat of other authors,
the eight-celled body at the end of the germ -tube is a sort of
protonema, from which the gamctophorc arises as a lateral
outgrowth. I have seen nothinji in the species under consider-
ation which supports such a view. licre the axis of growth
is continuous with that of the germ -tube, and in some cases
at least, and probably always, a single apical cell is developed

FiC- S, — Nicer ft AirM {Atx^t,). CermiDmbii iif ibt ^pore^, x 190. Ih K the figure at the left repre-
iAuti a surface vkw, the ane at the right ^ti optiiial ^cciLon ; K, gcrniLnAl tub^.

at the apex at a very early stage. Probably this initial cell
is one of the four terminal octant cells resulting from the
first divisions. This cell sometimes has but two sets of
segments cut off from it at firsts alternately right and left, but
whether this form is constant in the young plant I cannot
now say.

The four lower quadrants also divide, at first only by
trans%'ersc walls, and these cells lengthening give rise to a
cylindrical body composed of four rows of cells, terminated by
the more actively dividing group of cells at the summit. The
single apical cell is soon replaced by the group of initials found
in the full-grown gametophyte, and the method of growth from

MUSCINE^^HEPA TICjE—MARCHANTIACE^

now on is essentially the same. The growth of the cells in the
forward part of the dorsal surface of the young thallus is more
active than that of the ventral side, so that they project over
the growing point (Fig. 9), and as the outer cells of the lateral
segments of the apical cell (or cells) also increase rapidly in
size as they recede from the growing point, the forward margin

Fig. g.^Riccia hiria (Aust.). Later stages of germination. A, from below, X a6o ; B, optical section
of A, showing apical cell jr, X 520 ; C, X8s ; r, root-hairs.

of the thallus, seen from below, is deeply indented, and the
forward part of the thallus is thus occupied by a deep cavity, at
the bottom of which, toward the ventral side, lies the growing
point. This cavity is the beginning of the groove or furrow
found in the older thallus.

At first the cells of the young thallus are without inter-
cellular spaces, but at an early period (Fig. 9, C) the outer cells

MOSSES AND FERNS ^

of the young segments separate and form the beginnings of the
characteristic air-spaces. In R. hirta some of the dorsal cells
about the same time form short pointed papillae, the first indica-
tion of the pointed hairs characteristic of this species. As the
plant grows, new root-hairs are formed by the growing out of
ventral cells into papillae, which are cut off by a partition from
the mother cell. These first -formed root -hairs are always
smooth-walled, and it is only at a much later stage that the
other form develops, as well as the ventral lamellae, which are
quite absent from the young plant.

Classification of the Ricciacece

Besides the genus Riccia, which includes all but three species
of the family, there are two other genera, each represented by
a single species, which undoubtedly belong here. Of these
Ricciocarpus nutans is of almost world-wide distribution. It is
a floating form which, like Riccia fluitans^ only fruits when
growing upon the earth. Leitgeb ^ has made a very careful
study of the structure and development of the thallus, which
differs a good deal from that of Riccia^ in which genus this plant
was formerly placed. The apical growth is essentially the
same, and the differentiation of the tissues begins in the same
way, but the chlorophyll -bearing tissue is extraordinarily
developed. The air-spaces are formed in the same way as in
Riccia^ but they become very deep, and at an early stage, while
still very narrow, are divided by cellular diaphragms into several
overlying chambers, which, narrow at first, later become vfery
wide, so that the dorsal part of the thallus is composed of a
series of large polyhedral air-chambers arranged in several
layers, and separated by walls but one cell thick. The upper
chambers communicate with the outside by pores, quite like
those of the Marchantieae. The ventral tissue and midrib are
rudimentary, and the very long pendent ventral lamellae are
produced separately in transverse rows, which however become
displaced by the later growth of the thallus, so that their original
arrangement can no longer be made out. Oil-bodies like those
found in the Marchantieae occur. The fruiting plant, which
grows on the margins of ponds, etc. where the floating form is
found, is much more richly branched and more vigorous than
* Leitgeb (7), vol. iv.

II MUSCINE^— HEPATIC^— MARCHANTIACE^ 41

the floating form. The ventral scales become shorter, and
numerous wide but unthickened root-hairs are formed, which are
almost completely lacking in the floating form. The structure
of the reproductive organs and sporogonium are essentially the
same as in RicctUy except that the plants are strictly dioecious.

The third genus, Tesselina {Oxymitra\ represented by the
single species, T, pyramidata^ is much less widely distributed,
belonging mainly to Southern Europe, but also found in
Paraguay. This interesting form has also been carefully
examined by Leitgeb,^ who calls attention to its intermediate
position between the Ricciaceae and the Marchantieae. The
thallus has all the characters of the latter : air-chambers opening
by regular pores, usually surrounded by six guard-cells ; two rows
of ventral scales, independent from the beginning ; and the
sexual organs united into groups upon special parts of the
thallus. The sporogonium, however, is entirely like that of
Riccia^ so that it may properly be placed in the same family.
The plants are dioecious and strictly terrestrial.

A third genus, Cronisia^ represented also by a single species,
C paradoxa, is placed provisionally with the Ricciaceae by
Schiffner,^ but the structure and development have not been
investigated with sufficient completeness to make this certain.
It has been found only in Brazil. Schiffner says of this form :
" It belongs perhaps to the Corsinieae, and forms a direct
transition from the Ricciaceae 'to that family."

^ Leitgeb (7), vol. iv. p. 34. ' Schiffner (i), p. 15.

CHAPTER III

MARCHANTIEi4i:

Comparing the Marchantieae with the Ricciaceae, the close
similarity in the structure and development of the thallus is at
once apparent, but the former are more highly developed in all
respects. The development of definite air-chambers in the
green tissue, and a continuous epidermis with the characteristic
pores,- is common to all of them with the exception of the
peculiar genus Dumortiera, where the development of the air-
chambers is partially or completely suppressed. The genera
Ricciocarpus and Tessalina on the one hand, and Corsinia and
Boschia on the other, connect perfectly Riccia with the higher
Marchantiaceae as regards the structure of air-spaces and
epidermis, as they do in other respects. The epidermal pores
in the Marchantieae are sometimes simple pores surrounded by
more or less symmetrically arranged guard cells (Fig. lO, D),
or they are, especially upon the female receptacles, of a most
peculiar cylindrical form, which arises by a series of transverse
walls in the primary guard cells (Fig. lo, C). There is a good
deal of difference in the character of the air-chambers in
different genera. In Reboulia and Fimbriartd, for instance, they
resemble a good deal those of Ricciocarpus^ or more or less
complete division of the primary chambers being produced by
the formation of diaphragms or laminae, which give the green
tissue an irregular honey-combed appearance, and in these
forms there is not a sharp separation of the green tissue from
the central colourless tissue. In other genera, Marchantta^
Targionia (Fig. 1 6), Conocep/ialus, the dorsal part of the thallus
is occupied by a single layer of very definite air-chambers, each
opening at the surface by a single central pore. Seen from the

CHAP. Ill MARCHANTIE^ C 43

surface the boundaries of these spaces form a definite network
which in Conocephalus (Fig. i, D) is especially conspicuous.
The bottom of these chambers is sharply defined by the colourless
cells that lie below, and the space within the chamber is filled
by a mass of short, branching, conferva-like filaments, which in
the centre of the chamber have free terminal cells, but toward
the sides are attached to the epidermal cells and are more or
less confluent with the adjacent filaments.

As in Riccia root-hairs of two kinds are present, but the
thickenings in the tuberculate rhizoids (Fig. 11) are much
more pronounced, and these are not infrequently branched.

Fig. \o,~-Fimbriaria Cali/omica (Hampe). Development of the pores upon the archegonial
receptacle, X260. A, B, C, in longitudinal section ; D, view from ahove.

^nd may extend nearly across the cavity of the hair. The
ventral scales are not produced by the splitting of a single
lamella, as in Riccia, but are separate from the first and
usually arranged in two rows. Leitgeb^ recognises two
types of these organs. In their earliest stages they are alike,
and both arise from papillae close to the growing point. In
both cases this papillae is cut off from a basal cell, but in the
first type {Sauieria, Targionia, Dunwrtiera) it remains terminal,
usually forming the tip of a leaf-like terminal appendage of
the scale. In the second type, represented by most of the
other genera, this originally terminal papilla is forced to one
%ide by the development of a lateral appendage to the scale,

* Leitgeb (7), vol. vi. p. 17.

MOSSES AND FERNS

CHAP.

Fig. II. — Mar-
ckantia poly •
morpka (L.).
Part of a tubcr-
culate rhizoid,

which, arising at first from a single cell, rapidly increases in size,
and forms the overlapping dark purple marginal part of the
scale so conspicuous in many species.

^ ^ In different parts of the thallus are found large
mucilage cells, which are usually isolated, or in Cono-
cephaluSy according to Goebel's^ investigations, they
may form rows of cells which become confluent so
as to form mucilage ducts. In the earlier stages
these cells have walls not differing from those of the
adjacent cells, but as they grow older the whole cell
wall is dissolved, and the space occupied by the row
of young cells becomes an elongated cavity filled
with apparently structureless mucilage. These cells
are recognisable at an early period, as their contents
are much denser and more finely granular than
those of the adjacent cells. Small cells, each con-
taining a peculiar oil body, are found abundantly in
most species, both in the body of the thallus
and in the ventral scales. The structure and
development of these curious bodies, which are
found also in many other Hepaticae, have been
carefully studied by Pfeffer.^ The oil body has a round
or oval form usually, and in the Marchantieae usually is
found in a special cell which it nearly fills. It is brown or
yellowish in colour, and has a turbid granular appearance.
The extremely careful and exhaustive study of these bodies
by Pfeffer has shown that the oil exists in the form of an
emulsion in water, and that in addition to the oil and water
more or less albuminous matter is present, and tannic acid.
The latter is especially abundant in the oil bodies of Lunularia,
less so in Marchantia and Preissia.

The thallus of the Marchantiaceae is made up almost
entirely of parenchyma, but GoebeH states that in Preissia
commutata there are elongated sclerenchyma-like cells in the
midrib. The walls of the large colourless cells of the lower
layers of the thallus are often marked with reticulate
thickenings, which are especially conspicuous in Marchantia,

Most of the Marchantieae have no special non-sexu^I
reproductive organs, but in the genera Marchantia and
Lunularia special gemmae are produced in enormous numbers ;
1 Goebel (5), p. 531. ^ pfeflfe, (2). ' Goebel.

MARCHANTIE^

and in the latter form, which is extremely common in green-
houses, the plant multiplies only by gemmae, as the plants
are apparently all female. These gemmae, as is well known,
are produced in special receptacles upon the dorsal side of the
thallus. The receptacles are cup-shaped in Marchantia^ and
crescent-shaped in Lunularia^ where the forward part of the
margin of the cup is absent. These cups are apparently

Fig. 12. — Marckantia polymorpha (L.). A, Plant with gemma cups (>t, k\ X2 ; B-F, develop-
ment of the gemmae, X 525 ; G, an older gemma, X 360 ; v, t/, the two growing points.

specially developed air-chambers, which, closed at first, except
for the central pore, finally become completely open. The
edge of the fully-developed receptacle is fringed. The gemmae
arise from the bottom of the receptacle as papillate hairs, and
their development is the same in the two genera where they
occur. Fig. 1 2 shows their development in M. polyniorplia.

One of the surface cells of the bottom of the receptacle
projects as a papilla above the surface, ind is cut off by a
transverse wall -from the cell belqw. Thv outer cell next

46 MOSSES AND FERNS chap.

divides again by a transverse wall into a lower cell, which
develops no further, and a terminal cell from which the gemma
is formed. This terminal cell first divides into two equal cells
by a cross-wall (Fig. 1 2, B), and in each of these cells a siqiil^r
wall arises, so that the young gemma consists of four nearly
equal superimposed cells (Fig. 12, D). The wall III in Fig.
12, D, arises a little later than wall II, and is always more or
less decidedly concave upward. Each of the four primary cells
of the gemma is divided into two by a central vertical wall,
and this is followed by pbriclinal walls in each of the resulting
cells. At first the gemma is but one cell in thickness, but
later walls are formed in the central cells parallel to the
surface, so that it becomes lenticular. As it grows older there
is established on opposite sides (Fig. 1 2, G, z/, v') two growing
points, which soon begin to develop in the manner found in the
older thallus, and come to lie in a depression, so that the older
gemmae are fiddle-shaped. The gemma stands vertically, and
there is no distinction of dorsal and ventral surfaces. The
cells contain chlorophyll, except here and there the cells with
oil bodies, and an occasional large colourless superficial <:ell.
Among them are small club-shaped hairs, which secrete a
mucilage that swells up when wet, and finally tears away the
gemmae from their single-celled pedicels.

The further development of the gemmae depends upon their
position as to the light. Whichever side happens to fall down-
ward becomes the ventral surface of the young plant, and the
colourless cells upon this surface grow out into the first rhizoids.
The two growing points persist, and the young plant has two
branches from the first, growing in exactly opposite directions.
As soon as it becomes fastened to the ground the dorsiventrality
is established, and upon the dorsal surface the special green
lacunar tissue and the epidermis with its characteristic
pores are soon developed, while the ventral tissue loses its
chlorophyll, and soon assumes all the characters found in the
mature thallus.

's in most cases dichotomous,
- in Targionia (Fig. i, E), the

: nation of lateral adventitious

il surface.

the sexual organs correspond

B, but they are always formed

Th.

■ ".-hi\>- '»!

tiic iha'lw

as in V

*• -' ', *'l!t occ

nvAW^

growth

■■ .-. !> it

tc M<. K

brancl:

1 ■• '-c-d tVr.

:i \a .' '

"l.Ctn'. ^^

;].. •

closel}

t';.K . ti-

' v:

Ill MARCHANTIEJF. ^J

in more or less distinct groups or " inflorescences." As might
be expected, this is least marked in the lower forms, especially
the Corsinieae,^ where the main distinction between them and
the lower Ricciaceae is that in Corsinia the formation of sexual
organs is confined to a special region, and that the archegonia
do not have ^n individual envelope as in Riccia, but the whole
group of archegonia is sunk in a common cavity, which is of
exactly the same nature as that in which<each archegonium is
placed in the latter. In most of the Mafchantieae, however,
both antheridia and archegonia are borne in special receptacles,
which in the case of the latter are for the most part specially
modified branches or systems of branches, raised at maturity
lipon long stalks (Fig. 19). The antheridial receptacles are
sometimes stalked, but more commonly are sessile, and often
differ but little from those of the higher Ricciaceae.

The sporogonium shows an advance upon that of the
Ricciaceae by the development of a lower sterile portion, or foot,
in addition to the spore-bearing portion or capsule, and in the
latter there are always sterile cells, which in all but the lowest
Corsiniese have the form of elaters. At maturity, also, the ripe
capsule breaks through the calyptra, except in the Corsinieae,
where, too, the sterile cells do not develop into elaters, but
seem to serve simply as nourishing cells for the growing
spores. The stalk of the capsule is always short compared
with that of most Jungermanniaceae, and the wall of the capsule
remains intact until the spores are ripe.

The spores vary much in size, and in the development of
the outer wall. In Marchantia polymorpha and other species
where the spores germinate promptly, the ripe spore contains
chlorophyll, and the exospore is thin and slightly developed.
In such cases there is no distinct rupture of the exospore, but
the whole spore elongates directly into the germ - tube. (^Jix
ConocephaluSy where the spores are very large, the first divis^ns
occur in the spores before they are scattered. In species
where the spores do not germinate at once the process is
much like that of Riccia, and the thick exospore is ruptured and
remains attached to the base of the germ-tube.

The apical growth of the Marchantieae is very much like
that of Riccia, In Fimbriaria Californica (Fig. 13) the apical
cells seen in vertical section show the same form as those of

* Leitgeb (7), vol. iv.

AfOSSES AND FERNS

Riccia, and the succession of dorsal and ventral segments is
the same ; but here the development of the ventral segments
is much greater, and there is not the formation of the median
ventral lamellse as in Riccia, but the two rows of ventral scales
arise independently on either side of the midrib, very near the
growing point, and closely overlap and completely protect
the apex. The formation of the lacunae in the dorsal part
of the thallus begins earlier than in Riccia, and corresponds

very closely to what ob-

tains in Ricdocarpus, The
pits are at first very narrow,
but widen rapidly as they
recede from the apex. In
the epidermal cells sur-
rounding the opening of
the cavity, there are rapid
divisions, so that the open-
ing remains small and forms
the simple pore found in
this species. As in Riccto-
carpus, the original air-
chambers become divided
by the development of
partial diaphragms into sec-
ondary chambers, which are
not, however, arranged in
any regular order, and com-
municate more or less with

Fig. \i.—Fimbriaria Cali/omica (Hampe). A, Vcr- Qjig another
tical section through the apex of a sterile shoot, show-
ing the formation of the air-chambers ; x, the apical
cell, X 300 ; B, similar section through an older part
of the th.i11us, cutting through a pore, X 100.

In Targionia (Figs. 1 6,
17), where the archegonia
are borne upon the ordi-
nary shoots, the growth of the dorsal segments is so
much greater than that of the ventral ones that the upper
part of the thallus projects far beyond the growing point,
which is pushed under toward the ventral" side. A similar
condition is found in the archegonial receptacles of other forms,
where this includes the growing point of the shoot (Fig. 19).
In Targionia the lacunae are formed much as in Fimbriaria^
but they are shallower and much wider, and the pores corre-
spondingly few. The assimilative tissue here resem.Dles that

Ill MARCHANTIE^ 49

of Marchantia and others of the higher forms. It is sharply
separated from the compact colourless tissue lying below it,
and the cells form short confervoid filaments more or less
branched and anastomosing, and except in the central part of
the chamber united with the epidermal cells. Under the pore,
however, the ends are free and enlarged with less chlorophyll
than is found in the other cells.

All of the Marchantieae except the aberrant genus Dtt^or-
iiera correspond closely to one or the other of the above
types in the structure of the thallus, but in the latter the air-
chambers are either rudimentary or completely absent, and the
ventral scales are also wanting. Leitgeb^ investigated D.
irriguay whose thallus is characterised by a peculiar areolation
composed of projecting cell plates, and came to the conclusion
that these were the remains of the walls of the air-chambers,
whose upper parts, with the epidermis, were thrown off while
still very young. He had only herbarium material to work
with, but in this he detected traces of the epidermis and pores
in the younger parts. I examined with some care fresh
material of D. iricfiocephala, from the Hawaiian Islands, and
find that in this species, which has a perfectly smooth thallus
without areolations, that no trace of air-chambers can be
detected at any time. Vertical sections through the apex
show the initial cells to be like those of other Marchantiaceae,
and the succession of segments the same, but no indications
of lacunae can be seen either near the apex or fartl||f back,
the whole thallus being composed of a perfectly continuous
tissue without any intercellular spaces, and no distinct limit
between the chlorophyll -bearing and the colourless tissue.
As Dumortiera corresponds in its fructification with the higher
Marchantieae, the peculiarities of the thallus are probably to
be r^arded as secondary characters, perhaps produced from
the environment of the plant, and species like D, irrigua would
form transitional stages between the typical Mafchantiaceous
thallus and the other extreme found in D, trichocephala.

The structure and development of the sexual organs are
very uniform among the Marchantieae. In Fimbriaria Colt-
foTfiicay which is dioecious, the ahtheridial receptacle forms a
thickened oval disc just back of the apex. Not infrequently
(Fig. I, A), when the formation of antheridia begins not long

^ Leitgeb (7), vol. vi. p, 124.
E

MOSSES AND FERNS

CHAP.

before the forking of the thallus, both of the new -growing
points continue to develop antheridia for a time, and the
receptacle has two branches in front corresponding to these.
The receptacle is covered with conspicuous papillae which
mark the cavities in which the antheridia are situated. Verti-
cal longitudinal sections through the young receptacle show
antheridia in all stages of development, as their formation,
like those of Riccia, is strictly acropetal. The first stages
are exactly like those of Riccia^ and the primary cell divides
into two cells, a pedicel and the antheridium proper. The
divisions in the lower cell are somewhat irregular, but more
numerous than in Riccia, so that the stalk of the ripe anther-
idium is more massive (Fig. 14). In the upper cell a series

Fig. x^—t%nbriaria sp. (?). A, Part of a vertical section of a young antheridial r«ceptacle, showing
two very young antheridia ((J), X420 ; B-E, older stages.

of transverse walls is formed, varying in different species in
number, but more than in Riccia, and apparently always
perfectly horizontal. In Marc/ianiia polymorptia Strasburger ^
found as a rule but three cells, before the first vertical walls
were formed. In an undetermined species of Fimbriaria
(Fig. 14), much like F. Californica, the antheridia were un-
usually slender, and here frequently four, and sometimes five
transverse divisions are formed before the first vertical walls
appear. Sometimes all the cells divide into equal quadrants by
intersecting vertical walls, but quite as often this division docs
pot take place in the uppermost and lowest cell of the body
of the antheridium, or the divisions in these parts are more

^ Strasburger (2).

Ill

MARCHANTIEyE

irregular. The separation of the central cells from the wall
is exactly as in Riccia^ and the lower segments do not take
any part in the formation of the sperm cells, but remain as
the basal part of the wall. In Fitnbriaria the top of the
antheridium is prolonged as in Riccia, but in Marcliantia this
is not the case. The wall cells, as the antheridium^ approaches
maturity, are often much compressed, but in Targionia hypophylla.

Fig. 15. — Fitnbriaria Calijomica (Hampe). A, Longitudinal section of a fully -developed male re-
ceptacle, x8 ; B, longitudinal section of a nearly ripe antheridium, x 100 ; C, young sperm cells,
x6oo; D, spermatozoids, X1200.

where Leitgeb^ states that this compression is so great that
the cells appear like a simple membrane, I found that, so
far from this being the case, the cells were extraordinarily
large and distinct, and filled the whole space between the body
of the antheridium and the wall of the cavity, which in
Leitgeb's figures^ is represented as empty. The antheridium
becomes sunk in the thallus precisely as in Riccia, The sperm
cells are nearly cubical and the spermatozoid is formed in the

* Leitgeb (7), vol. vi. PI. X. Fig. 12.

Leitgeb, Lc,

52 SfOSSES ASD FERSS chap.

usual way. The free spermatozoid (Fig. 1 5, D) shows about
one and a half complete ttuns of a spiral. The cilia are very
lon^, and the vesicle usually plainly evident.

When the antheridia are borne directly upon the thallus,
the apical growth continues after antheridia cease to be formed,
and the receptacle \s thus left far back of the growing-in point.
In forms like Targionia^ however, where there are special
antheridial branches, the grdii-th of these is limited, and gener-
ally ceases with the formation of the last antheridia. The most
/specialised forms are found in the genus Marchantia and its
allies, where the antheridial receptacle is borne upon a long
stalk, which is a continuation of the branch from which it grows,
' and the receptacle is a branch-system. The growing point of
the young antheridial branch forks while still very young, and
this is repeated in quick succession, so that there results a
round disc with a scalloped margin, each indentation marking
a growing point, and the whole structure being equivalent to
such a branch system as is found in Riccia or Anthoceros^ where*
the whole thallus has a similar rosette -like form. The
antheridia are arranged in radiating rows, the youngest one
nearest the margin and the eldest in the centre. In some
tropical species, eg. M. geminaia, the branches of the
receptacle are extended and its compound character is
evident.

The archegonia are never sunk in separate cavities, but
stand free above the surface of the thallus. The simplest
form may be represented by Targionia, Here the archegonia
arise in acropetal succession from the dorsal segments of the
initial cells of the ordinary branches. A superficial cell
enlarges and is divided as in Riccia into an outer and an inner
cell. The latter undergoes irregular divisions arid its limits are
soon lost. In the outer cell the divisions occur in the same
order as in Riccia, but from the first the base of the archegonium
is broad and not tapering. Strasburger^ states that in
Marchantia there is a division of the outer of the two primary
cells by a wall parallel to the first, and that the lower one
forms the foot of the archegonium, and Janczewski ^ gives the
same account of the young archegonium of Preissia commuiata.
This certainly does not occur in Targioniay and to judge from
the later stages of Fimbriaria Calif omicay this species too lacks
* Stra§burger (2), p. 416. ■ Janczewski (i), p. 386r

{

Ill

MARCHANTIEjE

this division. The full-grown archegonium is of more nearly
uniform thickness than in Riccia^ as the venter does not become
so much enlarged. The neck canal cells are more numerous,
about eight being the common number, but in Targionia the
formation of division walls between these is sometimes sup-

Fig. 16. — Targionia hypofhyllaiX,.}. A, Longitudinal section of the thallus, X 100 ; ar, archegonia ; //,
ventral scales; B, median section through a pore, showing the assimilating cells {cl) below, X300.

pressed (Fig. 17, C), so that this may account for Janczewski's^
error in stating that the number was always four, as the nuclei
in unstained sections might be very easily overlooked. The
cover cells are somewhat smaller than in Riccia and do not
usually undergo as many divisions, there being seldom more

* Janczewski (i), p. 386.

MOSSES AND FERNS

than six^ in all. In Targionia (Fig. 21, A), and Strasburger^
observed the same in Marc/tantia, the ripe egg shows a distinct
"receptive spot," that is, the upper part of the unfertilised
egg is comparatively free from granular cytoplasm, while the
lower part, about two-thirds in Targionia, is much more densely
granular. The nucleus is not very large and has very little
chromatin. The nucleolus is large and distinct and stains very
intensely. As the archegonium of Targionia matures, its
neck elongates rapidly and bends forward and upward, no

Fig. ij.—Tar^onia hypophylia (L.). A, Longitudinal section of the apex of the thallus, with young
archegonia (tfy), X525; x^ the apical cell; B, ypung; C, older archegonium in longitudinal
section ; D, cross-section of the archegonium neck, X 525.

doubt an adaptation to facilitate the entrance of the sper-
matozoid. A similar curving of the archegonium neck is
observed in other forms where the archegonium is upon the
lower side of the receptacle.

After an archegonium (or sometimes several of nearly
equal age) is fertilised, the growth in length of the thallus stops,
but there is a rapid lateral growth with results in the formation
of two valves, which meet in front much like the two parts of
a bivalve shell, and this involucre completely encloses the
young growing sporogonium.

^ Strasburger (2), p. 418.

MARCHANTIEJE

In the simplest cases, where the archegonia are borne upon
a receptacle ^ which is raised upon a stalk, e^, Plagiochasma,
Clevea (Fig. i8, A), the receptacle does not represent, according
to Leitgeb,* a complete branch, but is only a dorsal outgrowth-
of the latter, which may gfbw out beyond it, or even form
several receptacles In succession. The first indication of the
receptacle is a dor-

sal prominence which
soon becomes almost
hemispherical, and
near the hinder margin
the first archegonium
arises, without, appar-
ently, any special re-
lation to the growing
point On the lat-
eral margins are then
formed two other arche-
gonia, not, however,
simultaneously ; and
finally a fourth may be
formed in front : three
or four archegonia
in all seem to be the
ordinary number. The
stalk of the receptacle

is also a dorsal append- ^'^' *^* — ^* Clev«a sp, a, longitudinal section of the thallus

e \^ L 1 1 ' J showing the dorsal origin of the female receptacle ( 9 ) ; v^

age of the thallus, eind the growing point (diagram after Leitgcb); B, Rebaulia

not a direct continua-
tion of it.

The next type
is that which Leitgeb^ attributes to Grtmaldia, Reboulia,
Fimbriaria, and some others, but it is not the type found
in Fimbriaria Calif arnica. In this type the structure of
the receptacle and the origm of the archegonia are the same
as in that just described ; but here the growing point of
the branch forms the forward margin of the receptacle,
and the stalk is a direct continuation of the axis of the

* The sporogonial receptacle of the Marchantieae is sometimes known as the
Carpocephalum.

^ Leitgeb (7), vol vi. p. 29. ' Leitgeb, l,c, p. 30.

hemispfutrica (Radd.), longitudinal section of very young
receptacle with the first archegonium (9)i -^i the apical
cell, X 300 (after LeitgebX

MOSSES AND FERNS

branch. Upon its ventral surface it shows a furrow in which
root-hairs are produced in great numbers, and this furrow

Fig. 19. — Fimthrimrim CmH/grmicm (HampeX A« Plant with tvo fblly-srovn sporogooijJ ncxptiuAes^
itttafml sue; B» asanglereccpc^dc, X4 ; C, the satoke cut k>ngitudiiuJIy, sfaovinrthe sporogooioin
{jsp\ cadosed in the perianth {/er) ; D, nearly median aectioii of a yonsK necqitacle showing one
frowing point (.r) lad an archegooiom («r)^ L, airspnces; «/, a pore; r, rhiaoids, X40; £,
the frowing point of the sasK with an archegonhan, X300 ; jr, the apical cell.

passes over into the ventral surface of the thallus (Fig.
19. B).

in MARCHANTIE^ - 57

The highest type is that of Leitgeb's ^ " Compositae." Here
the female receptacle is a branch system similar to that of the
riTale receptacle ' of Marchantia, The branching is usually
completed at a very early period, while the receptacle is almost
concealed in the furrow in the front of the thallus. A simple
case of this kind is seen -in Fimbriaria Calif omica (Fig. 19).
Here there are four growing points that have arisen from the
repeated dichotomy of the primary growing point of the branch,
and each of these gives rise to archegonia in acropetal succession,
much as in Targionia, but the number of archegonia is small,
not more than two or three being as a rule formed from each
apex. The development of the dorsal tissue is excessive and
the ventral growth reduced to almost nothing, and the growing
apices are forced under and upward and lie close to the stalk,
and the archegonia have the appearance of being formed on the
ventral side of the shoot, although morphologically they are
dorsal structures. In the common Marchantia polytnorpha the
branchdj character of the receptacle is emphasised by the
development of the " middle lobe " between the branches.
These lobes grow out into long cylindrical appendages between
the groups of archegonia, and give the receptacle a stellate
form. Usually in M, polytnorpha there are eight growing
points in the receptacle, and of course as many groups of
archegonia, which are much more numerous than in any other
genus, amounting to a hundred or more in one receptacle. In
Marchantia^ as well as some other genera with compound
receptacles, there are two channels in the stalk, showing that
this is here influenced by the first dichotomy. While the
archegonia, before fertilisation, are quite free, the whole group
of archegonia, and indeed the whole receptacle, is invested with
hairs or scales of various forms that originate either from the
epidermis of the dorsal side, or as modifications of the ventral
scales.

The lacunar tissue is very much developed upon the
receptacles, as are to an especial degree the peculiar cylindrical
breathing pores. The formation of these begins in the same
way as the simple ones, being merely the original opening to
the air-space. This seen from the surface shows an opening
with usually five or six cells surrounding it. Vertical sections
show that very soon the cells surrounding the pore become

^ Leitgcb (7), vol. vi. p. 33.

58 MOSSES AND FERNS chap.

deeper than their neighbours and project both above and below
them. In these cells next arise (Fig. lo, A, B) a series of
inclined walls by which each of the original cells is transformecl
into a row of several cells, and these rows together form a
curious barrel-shaped body surrounding the pore. The upper
cells converge and almost close the space above, and this is still
further diminished by the cuticle of the outer cell wall of the
uppermost cells growing beyond the cells and leaving simply
a very small central opening. The rows of cells also converge
below, and in Fimbriaria Califomica the lowermost cells are
very much enlarged, and probably serve to close the cavity
completely at times, and act very much like the guard cell
of the stomata of vascular plants. In Leitgeb's group of the
Astroporae, the simple pores of the thallus have the radial
walls of the surrounding cells strongly thickened, so that the
pores seen from the surface appear star-shaped. The most
specialised of the MarchantiecB^ ix, Marchantia^ Lunulariay etc.,
have the cylindrical pores upon the vegetative part of tl^ thallus
as well-as upon the receptacle, but in the others they* occur
only upon the latter.

The Sporogonium

The first divisions in the embryo of the Marchantiea are
the same as in the Ricciacese, but only the upper part (dapsule)
of the sporogonium develops spores, while the rest be^:tJmes
stalk. The simplest form of capsule is found in the genera
Corsinia and Boschia, which have been carefully studied- by
Leitgeb.^ In these the embryo, instead of remaining globular
as it does in Rtccia, elongates and very early becomes differenti-
ated into a nearly globular upper part, or capsule, and a usually
narrower basal portion, the stalk (Fig. 20). In the capsule
at a very early period a single distinct layer of outer cells is
separated from the central group of cells, and forms the wall of *
the capsule, which in Boschia at maturity develops upon the
inner cell walls thickened bars. Only a portion of the cells of
the central part produce spores ; the remainder do not divide
after the spore mother cells are formed, but remain either as
simple slightly elongated nourishing cells {Corsinia) or elaters

{Boschia),

^ Leitgeb (7). vol. iv. pp. 45-47.

MARCHANTIEAL

The other Marchantieae are much alike, and as Targionia
was found to be an especially satisfactory form for study, on
account of the readiness with which straight sections of the
embryo could be made, it was taken as a type of the higher
Marchantieae. The first division wall (basal wall) is trans-
verse, and divides the embryo into two nearly equal parts.
This is followed in both halves by nearly vertical walls
(quadrant walls), and these and the basal wall are then
bisected by the octant walls, so that as in Riccia the young
embryo is formed of eight nearly
equal cells. In Targionia, even at this
f)eriod, the embryo is always somewhat
elongated instead of globular. The
next division walls vary a good deal
in different individuals. Fig. 21, C
shows a very regular arrangement of
cells, where the first divisions were
much the same in all the quadrants.
Here all the secondary walls were
nearly parallel with the basal wall, and
intersected the quadrant and octant
walls ; but quite as often, especially in
the upper half of the embryo, these
secondary walls may intersect the basal
wall. In no cases seen was there any
indication of a two-sided apical cell
such as Hofmeister^ figures for Targi-
onia, and probably his error arose from
a study of forms where the quadrant
walls were somewhat inclined, in which
case the intersection of one of the secondary walls with
it might cause the apex of the embryo to be occupied by
a cell that, in section, would appear like the two-sided
apical cell of the Moss embryo. The regular formatiqji of
octants was observed by me in Fimbriaria Califomica,
and by Kienitz-Gerloflf^ and others in Marcluxntia, Grimaldia,
and Preissia, and probably occurs normally in all Mar-
chantiaceae.

After the first anticlinal walls are formed in the octants, no
definite order could be observed in the succeeding cell divisions,

' Hofmeister (i), PI. XV. Figs. 24, 25. » Kienitz-Gerloff (i, 2).

Fig. ao. — Cortinia marchaniioids
(Radd). Young sporogonium,
optical section, X 300 (Leitgeb).

MOSSES AND FERNS

CHAP.

especially in the lower half of the embryo. In the upper part
pericHnal walls appear, but not at any stated time, so far as
could be made out, and the first ones do not, as Leitgeb asserts,

Fig. ^x,—Targumia hypophylUt (L.). A, Longitudinal section of the venter of a ripe archegoniam,
X500: B-E, development of the embryo, seen in longitudinal median section — B, two<elled,
D, four-celled stages, X500, except E, which is magnified 150 times : F, nearly median section of
the upper part of an older embryo, X 250.

necessarily determine the separation of the archesporium, as in
the Corsinieae. The growth now becomes unequal, tRe cells in
the central zone not dividing so actively, a marked constriction

Ill

MARCHANTIE^

is formed, and the young sporogonium becomes dumb-bell
shaped. By this time a pretty definite layer of cells (Fig.
21, F) is evident upon the outside of the capsule, but the
cells of the globular lower part, or foot, are nearly or quite
uniform. They are larger than those of the caps\ile, and more
transparent. In the latter the wall becomes later more definite,
and remains but one* cell thick until maturity. The arrange-
ment of the cells of the archesporium is very irregular, and until
the full number of these is formed they are all much alike.

Fig. 32. — Targionia hypopkylla (L.X A, Median longitudinal section of older embryo enclosed in the
calyptra (co/), X 80 ; B, a portion of the upper part of the same embryo, X 480 ; the nucleated
cells represent the archesporium ; C, part of the archesporium of a still later stage ; //, elaters ;
j/^, sporogenous cells, X480.

Just before they separate, however, careful observation shows
that two well-marked sorts of cells are present, but intermingled
in a perfectly irregular way. A part of these cells are nearly
isodiametric, the others slightly elongated, and the nucle;i of the
former cells are larger and more definite than those of the
latter. At this stage the cells begin to separate by a partial
deliquescence of their cell walls, and when stained with
Bismarck-brown these mucilaginous walls colour very deeply,
and the cells are very distinct in sections so treated. They
finally separate completely, and the much -enlarged globular

MOSSES AND FERNS

capsule now contains a mass of isolated cells of two kinds,
globular sporogenous cells and elongated elaters. The former
now divide into four spores, but before the nucleus divides
the division of the spores is indicated by ridges which project
inward and divide the cavity of the mother cell almost com-
pletely.

With the first divisions in the embryo the venter of the
archegonium, which before was only one cell thick, divides by
a series of periclinal walls into two layers of cells, which later
undergo further divisions, so that the calyptra surrounding the

Fio. ^i.—Fimbriaria Califomica (HampeX A, Young, B, older embryo in median section. A,
X300 ; B, X 100; C, upper part of a sporogonium, aHer the diflferentiation of the archesporiuxn,
X200.

older capsule may consist of four or more layers of cells. The
neck of the archegonium remains unchanged, but the tissue of
the thallus below the archegonium grows actively, and surrounds
the globular foot, which has grown down into the thallus for
some distance, and only the capsule remains within the
calyptra. This large growth of the foot is at the expense of
the surrounding cells of the thallus, which are destroyed by its
growth, and through the foot nourishment is conveyed from the
thallus to the developing capsule. That is, the sporogonium is
here a strictly parasitic organism, growing entirely at the
expense of the thallus.

MARCHANTIEJL 63

The further growth of the spores and elaters was studied in
Fimbriaria Californica, The spores remain together in tetrads,
until nearly ripe. In sections parallel to the surface of the
younger spores (Fig. 24, C) the outer surface, of the exospore
is covered with very irregular sinuous thickenings, at first
projecting but little above the surface, but afterward becoming
in this species extraordinarily developed. In sections of the
ripe spore (Fig. 24, D) three distinct layers are evident, the
cellulose endospore, the thick exospore, and this outer thickened

Fig. 24. — Fimbriaria Cali/omica (Hampe). A, Young elater x6oo; B, a fully -grown elater,
X 300 ; C, surface view of the wall of a young spore, showing the developing episporic ridges,
X 60c ; D, section of the wall of a ripe spore, X 300. <

mass of projecting ridges which has every appearance of being
deposited from without, and must therefore be characterised as
epispore (perinium) ; Leitgeb ^ distinctly states that thickenings
of this character do not occur in the Marchantieae, but that the
thickenings are always of the character of those in Riccia,

The elaters are at first elongated thin-walled cells with a
distinct although small nucleus, and nearly uniformly granular
cytoplasm. As they grow the cytoplasm loses this uniform
appearance, and a careful examination, especially of sections,
shows that the granular part of the cytoplasm begins to form

^ Leitgeb (7), vol. vi. p. 45.

64 MOSSES AND FERNS chap.

a spiral band, recalling somewhat the chlorophyll band of
Spirogyra, This is the beginning of the characteristic spiral
thickening of the cell wall, and while at first irregular, the
arrangement of the granular matter becomes more definite, and
following the line of this spiral band of granules in the
cytoplasm, there is formed upon the inner surface of the wall
the regular spiral band of the complete elater. This band,
which is nearly colourless at first, becomes yellow in the mature
elater, and in Targionia^ where there are generally two, they are
almost black. Not infrequently branched elaters are found,
but these are unicellular, and no doubt owe their peculiar form
to their position between the spore mother cells in the young
archesporium. An axial row of granules, which seem to be of
albuminous nature, remains in the elaters of Fimbriaria until
maturity.

The differences in the structure of the sporogonium in
different genera of the Marchantieae are slight. In Marchantia
polymorpha, the young sporogonium is nearly globular, and even
when full grown it is ellipsoid with the stalk and foot quite
rudimentary. Most forms, however, have the foot large, but
the stalk, compared with that of most Jungermanniaceae, is
short. In most of them the whole of the upper half of the
young embryo develops into the capsule, but in Fimbriaria
Californica I found that the archesporium was smaller than in
other forms described, and that sometimes the apical part of
the sporogonium was occupied by a sort of cap of sterile cells
(Fig. 23).

The dehiscence of the capsule is either irregular, e^.
Targioniay or by a sort of lid, e,g, Grimaldia^ or by a number
of teeth or lobes, e.g. Lunularia, Marchantia, In «ome forms
after fertilisation there grows up about the archegonium a cup-
shaped envelope," perianth, pseudoperianth," which in Fimbriaria
especially is very much developed, and projects far beyond the
ripe capsule (Fig. 19).

The germination of the spores corresponds in the main with
that of Riccia. Except in cases where the exospore is very
thin, in which case it is not ruptured regularly, the exospore
either splits along the line of the three converging ridges upon
the ventral surface, and through this split the endospore
protrudes in the form of a papilla, as in Riccia ; or in Targionia
(Fig. 25) the exospore is usually ruptured in two places on

Ill

MARCHANT/EyE

opposite sides of the spore, and through each of these a filament
protrudes, one thicker and containing chlorophyll, the other
more slender and nearly colourless. The first is the germ tube.

Fig. 35. — Targionia hypcphyllaiX*.). Germination of the spores, X about aoo. In B two germ tubes
have been formed ; C and £ are optical sections ; x^ apical cell ; r, primary rhizoid ; sp^ spore
membrane.

the second the first rhizoid. In Fimbriaria Calif omica the
first root-hair does not usually form until a later period. In
Targionia a curious modification
of the ordinary process is quite
often met with (Fig. 25, B). Here,
by a vertical division in the very
young germ tube, it is divided into
two similar cells, which both grow
out into germ tubes. Whether
both of these ever produce perfect
plants was not determined, but the
first divisions in both were per-
fectly normal. The first divisions
in the germ tube are not quite

,c • r> • • 7 • ^ u i Y\c,.^.— Targionia hypophylla (X..). Germ

so uniform as in Rtccia hirta, but p,a„j i„ ^hich the thaiius en has been
resemble them very closely in the formed secondarily, xa6o.
commoner forms.

In Fimbriaria especially, and this has also been observed in

Fig. 27. — Ftmbriaria Cali/omica (Hanipe). A, B, Young plants in optical section^ showing the
single two-sided apical cell (jr), X 360 ; C, horizontal section of an older plant with a single four-
sided initial {x\ X425 ; D, £, two young plants, D from below, £ from the side, X85.

CHAP. Ill MARCHANTIE^ 67

Marchantia^ and other genera, a distinct two-sided apical cell
IS usually developed at an early period, and for a time the
growth of the young plant is due to the segmentation of this
single cell. Finally this is replaced by a single four-sided cell
(Fig. 27, C), very much like the initial cell of the mature
thallus. The young plant, composed at first of homogeneous
chlorophyll - bearing cells, grows rapidly and develops the
characteristic tissues of the older thallus. The first rhizoids
are always of the simple form, and the papillate ones only
arise later, as do the ventral scales. Targionia shows a number
of peculiarities, being much less uniform in its development
than Fimbriaria. While it often forms the characteristic
germ tube, and the divisions there are the same as in Riccia and
Fimbriaria^ the formation of a germ tube may be completely
suppressed, and the first result of germination is often a cell
mass, from which later a secondary germ tube may be formed
with the young plant at the apex (Fig. 26). Such cases as
these are the only ones where it seems really proper to speak of
the plant arising secondarily from a protonema, for in other
cases, as in Ricda^ the growth is perfectly continuous, and the
axis of the young thallus is coincident with that of the germ
tube, and in no cases observed by me could it in any sense be
looked upon as a secondary lateral growth.

Classification of the Marcftantiea

The higher Marchantieae are readily separable into three
families, the Corsinieae, Targionieae, and the true Marchantieae.
Leitgeb has made a further division of the latter family, but
some of the characters given are not sufficiently constant to
warrant his division, and for that reason it has been thought
best not to accept them.^ Thus Fimbriaria Californica, which
is, in regard to its fructification, typical, has the female recep-
tacle of the composite type, a character which, according to
Leitgeb, not only does not belong to the genus Fimbriaria^ but
is not found in any genus of the group (Operculatae) to which
he assigns it. This species too does not have the capsule
operculate, but opens irregularly. The Corsinieae, as we have

1 Leitgeb (7), vol. vi. PI. IX. Fig. 13.
* Leitgeb (7) and Schiffher (i), p. 24.

68 MOSSES AND FERNS chap.

already seen, are exactly intermediate in character between the
highest Ricciaceae, such as Tessalituiy and the lower Marchantieae,
and this is true both of the structure of the thallus and the
sporogonium. Corsinia differs from all the higher Marchantieae
in the character of the ventral scales, which are formed in more
than two rows, like those of Ricciocarpus, Boschia, the other
genus, has two rows of scales of the ordinary form. The
archegonia are borne in a group in a depression upon the
dorsal surface of the thallus, but are not formed upon a special
receptacle, although after fertilisation the cells at the bottom of
the cavity multiply actively and form a small prominence upon .
which the young sporogonia are raised, and this may perhaps
be the first indication of the archegonial receptacle in the other
forms.

The TargioniecB include the two genera Targionia^ which
has been already described at length, and Cyathodium} a genus
whose development is not sufficiently known to make its
systematic position quite certain. In the position of the sexual
organs, and the formation of the two-valved involucre about
the fruit, as well as the position of the latter, it corresponds
closely to Targionia, but the structure of the thallus is
extraordinarily simple, there being practically but two layers of
cells with large irregular air-chambers between. While two
sorts of rhizoids are present, those that represent the papillate
type of the other Marchantiaceae, while thicker walled than
the others, do not develop the projecting prominences.
Indeed the whole structure of the plant is curiously reduced,
and Leitgeb describes it as resembling the young plants of
Marchantia or Preissia. The development of the sexual
organs is but imperfectly known, and the suggestion of
Leitgeb's, that possibly the antheridium is reduced to a single
cell, seems hardly probable in view of the structure of the rest
of the plant The spOrogonium has the stalk and foot exceed-
ingly rudimentary, but the upper part of the capsule shows a
zone of cells whose walls are marked by peculiar ring-shaped
thickenings, and opens regularly by a number of teeth, which
on account of the thickened bars upon the cell wall offer a
superficial resemblance to the peristome of the Bryineae. As
in Targionia the archegonia arise near the apex of the ordinary
shoots, and no proper receptacle is formed.
* Leitgeb (7), vol. vi. p. 136.

Ill MARCHANTIE^ 69

All of the other forms have the archegonia borne upon a
special receptacle, which, as the sporogonia develop, is raised
upon a stalk. Here belong, according to Schiffner,^ sixteen
genera with about 150 species. The receptacle may be, as we
have seen, strictly dorsal in origin, or it may include the
growing point of the archegonial branch, or finally it may be
a branch system arising from the repeated dichotomy of the
original growing point.

Resume of the Marcliantiacece V

Comparing the different members of this order, one is
struck by the almost imperceptible gradations in structure
between the different families, and this accounts for the
difference of opinion as to where certain genera belong.
That the Ricciaceae cannot be looked upon as a distinct
order is plain, and they may perhaps be best regarded
as simply a family co-ordinate with the Corsinieae and
Targionieae, and not a special group opposed to all the other
Marchantiaceae. The gradual increase in complexity of
structure is evident in all directions. First the thallus passes
by all gradations from Riccia — with its poorly defined air-
chambers with no true pores and single ventral lamellae,
through Ricciocarpus and Tesscdina^ where definite air-chambers
are present, opening by pores of the same form as those of
the lower Marchantieae, and separate ventral scales occur — to
forms like Marchantia, where the air-chambers are very definite
and contain a special assimilating tissue, and the pores are of
the cylindrical type. With this differentiation of the thallus
is connected the segregation of the sexual organs and the
development of special receptacles upon which they are borne.
Finally, in the development of the sporogoriium, while there is
almost absolute uniformity in the earlier stages, we find a
complete series of forms, beginning with Riccia^ where no stalk
is developed and all the -cells of the archesporium develop
spores, ascending through Tessalina^ with a similar absence of
a stalk, but the first indication of sterile cells, through the
Corsiniece, to forms with a massive foot and elaters fully
developed. It may be said, however, that there is no

^ Schiffner (i), p. 25.

70 MOSSES AND FERNS chap, hi

absolute parallelism between the development of the gameto-
phyte and that of the sporophyte, for in Marchantia, the most
specialised genus as to the gametophyte, the sporogonium is
less developed than in the otherwise simpler Targionia and
Fimbfiaria,

CHAPTER IV

THE JUNGERMANNIACEiE

A VERY large majority of the Hepaticae belong to the
Jungermanniaceae, which show a greater range of external
differentiation than is met with in the Marchantiaceae, but less
variety in their tissues, the whole plant usually consisting of
almost uniform green parenchyma. In the lowest forms, e.g,
Aneura^ and Metzgeria^ the gametophyte is an extremely
simple thallus, in the former composed of almost perfectly
similar cells, in the latter showing a definite midrib. Starting
with these simplest types, there is a most interesting series of
transitional forms to the more specialised leafy ones, where,
however, the tissues retain their primitive simplicity. All of
the Jungermanniaceae grow from a definite apical cell, which
differs in form, however, in different genera, or even in different
species of the same genus. Root-hairs are usually present,
but always of the simple thin-walled type.

The gametophyte, with the exception of the genera Haplo-
mitrium^ Calobryum^ and Riella, is distinctly dorsiventral, and
even when three rows of leaves are present, as in most of the
foliose forms, two of these are dorsal and lie in the same plane,
while the third is ventral. In the thallose forms, while the
bilaterality is strongly marked, there is not the difference
between the tissues of the dorsal and ventral parts which is so
'marked in the Marchantiaceae. In the lowest forms the
gametoph)rte is a simple flat thallus fastened to the substratum
by simple root-hairs, and develops no special organs except
simple glandular hairs which arise on the ventral side near the
apex, and whose mucilaginous secretion serves to protect th^"
growing point. In Blasia and Fossombrania we have genera

72 MOSSES AND FERNS chap.

that, while still retaining the flattened thalloid character, yet
show the first formation of lateral appendages which represent
the leaves of the true foHose forms. In the latter the axis is
slender, and the leaves usually in three rows and relatively large.

The archegonia correspond closely in their development to
those of the Marchantiaceae, and in the lower (anacrogynous)
forms arise in much the same way from surface cells of the
dorsal part of the younger segments, and the apical cell is not
directly concerned in their formation. The archegonia in
these thus come to stand singly or in groups upon the
dor^l surface of the thallus, whose growth is not interrupted
by their development. In the higher leafy forms (Junger-
manniaceae acrogynae) they occur in groups at the end of
special branches, whose apical cell finally itself becomes the
mother cell of an archegonium, and with this the growth in
length of the branch ceases.

The antheridia differ essentially in their first divisions from
those of the Marchantiaceae. After the first division in the
mother cell, by which the stalk is cut off from the antheridium
itself, the first wall in the latter, in all forms investigated
except SpfuBTocarpus and Riella^ is vertical, instead of horizon-
tal, and the next formed walls are also nearly vertical. The
ripe antheridium is usually oval in outline and either nearly
sessile or provided with a long pedicel. The spermatozoids
are as a rule larger than in the Marchantiaceae, and show more
numerous coils, but like them are al^(rays biciliate.

The embryo differs in its earliest divisions from that of the
Marchantiaceae. The first transverse wall divides the embryo
into an upper and lower cell, but of these the lower one, except
in SplKBTocarpus and Riella, takes no further part in the
development of the sporogonium, but either remains undivided
or divides once or twice to form a small appendage to the base
of the sporogonium. In the upper cell the first wall may be
either vertical {i,e, Pellia and most anacrogynous forms), or it
may be transverse. From the upper of the two primary cells
not only the capsule but the stalk and foot as well are formed.
The development of these different parts varies in different
forms, and will be taken up when considering these.

All of the Jungermanniaceae, except the Rielleae, possess
perfect elaters, but in the latter these are represented merely
by sterile cells that probably serve simply for nourishing the

IV THE JUNGERMANNIACEM 73

growing spores. The sporogonium remains within the calyptra
until the spores are ripe, when by a rapid elongation of the
cells of the seta it breaks through the calyptra, which is left at
its base, and the capsule then opens. The opening of the \
capsule is usually effected by its walls splitting into four valves/
along lines coincident with the first formed vertical cell walls j
in the young embryo. These valves, as well as the elaters, are
strongly hygroscopic, and by their movements help to scatt.er
the ripe spores. The latter show much the same differences
observed in the Marchantiaceae. When the spores germinate
at once they have abundant chlorophyll and a thin exospore,
but where they are exposed to drying up, they have no
chlorophyll and the exospore is thick and usually with
characteristic thickenings upon it. From the germinating
spore the young gametophyte may develop directly, or there
may be a well-marked protonemal stage. This latter is
always found in the foliose forms, and is either a flat thallus,
like the permanent condition of the lower thallose genera, or
sometimes {Protocephalozid) it is a branched filamentous
protonema, very much like that of the Mosses, and sometimes
long-lived and producing numerous gametophores.

Non-sexual reproductive bodies in the form of unicellular
gemmae are found in many species, and in Blasia special
receptacles with multicellular gemmae something like those of
MarcJtantia occurs

The Jungermanniaceae naturally fall into two well-marked
series,^ J. anacrogynae and J. acrogynae, based upon the position
of the archegonia. These in the former are never produced
directly from the apical cell of a branch, in the latter group
the apical cell of the archegonial branch always sooner or later
becomes transformed into an archegonium. The Haplomitrieae
show some interesting intermediate forms between the two
groups, but all the other Jungermanniaceae examined belong
decidedly to one or the other. As a rule the Anacrogynae
are thallose (the "frondose" forms of the older botanists),
but a few genera, especially Fossombronia^ show a genuine
formation of leaves. All the Acrogynae have a distinct slender
stem with large and perfectly developed leaves.

^ Pro£ L. M. Underwood proposes the name Metzgeriaceae for the J. anacrogynae,
reserving the name Jungermanniaceae for the J. acrogynae. These two groups he
considers co-ordinate with the Marchantiaceae and Anlhoceroteae.

MOSSES AND FERNS

CHAP.

Jungermanniacece Anacrogynce

The simplest form belonging here is Sphcerocarpus^ a plant
that shows certain affinities with the Ricciaceae, but on the whole
seems to be more properly placed at the bottom of the series
of the Jungermanniaceae. 5. terrestris is a small plant growing
upon the earth, usually in crowded patches, where, if abundant.

c $

Fin. 28. — Spfuervcarpus terrestris var. Ca/i/ornicus (Aust.). A, Male plant, X40 ; (^ , anthertdia ; B,
median section of a similar plant, X 80 ; C, the apex of the same section, X 240 ; A, ventral hair.

it is conspicuous by the bright green colour of the female
plants. The males are very much smaller, often less than a
millimetre in diameter, and purplish in colour, so that they are
easily overlooked. The thallus is broad and passes from an
indefinite broad midrib into lateral wings but one cefl in
thickness (Fig. 28). The forward margin is occupied by a

IV THE JUNGERMANNIACE^ 75

number of growing points formed by the rapid dichotomy of
the original apex, and separated only by a few rows of cells.
From the lower side of the thallus grow numerous root-hairs
of the thin-walled form. The whole upper surface is covered
with the sexual organs, each of which is surrounded by its own
very completely developed envelope.

M |^> A vertical section passing through one of the growing
points (Fig. 28, C) shows a structure closely like a similar
section of Riccia, The apical cell {x) produces dorsal and
ventral segments, and from the outer cells of the former the
sexual organs arise exactly as in Riccia, On the ventral
surface the characteristic scales of Riccia are absent, and are
replaced by the glandular hairs found in most of the anacro-
gynous Jungermanniaceae.

The development of the archegonium shows one or two
peculiarities . in which it differs from other Hepaticae. The
mother cell is much elongated, and the first division wall, by
which the archegonium itself is separated from the stalk, is
some distance 'above the level of the adjacent cells of the
thallus, so that the upper cell is very much smaller than the
lower one. The upper cell has much denser contents than the
lower one, which instead of remaining undivided as in Riccia,
divides into two nearly equal superimposed cells, this division
taking place dbout the same time as the first division in the
archegonial cell (Fig. 29, B). The divisions in the latter ard
the same as in Riccia, and the general structure of the arche-
gonium offers no noteworthy peculiarities. The number of
neck canal cells is small, probably never exceeding four, and in
this respect recalls again Riccia, The central cell is relatively*
large, and the ventral canal cell often nearly as large as the
^g. As the archegonium develops, its growth is stronger on '
the posterior side, and it thus curves forward. At first the
young archegonium projects free above the surface, but
presently an envelope is formed about it exactly as in Riccia,
but arising at a later^ stage. After this has begun to form, its
growth is very rapid, and it soon overtakes the archegonium
and grows beyond it, and finally forms a vesicular body,
plainly visible to the naked eye, at the bottom of which the
archegonium lies. The formation of this involucre is quite
independent of the fertilisation of the archegonium, and as
these peculiar vesicles cover completely the whole dorsal

MOSSES AND FERNS

surface of the plant, they give it a most characteristic
appearance. Usually each archegonium has its own envelope,
but Leitgeb ^ states that two or even more may be surrounded
by a common envelope. When ripe, the venter of the arche-
gonium is somewhat enlarged, but not so much as in Riccia.
The egg-cell is very large, oval in form, and nearly fills the
cavity of the single-layered venter.

The first wall in the embryo is transverse, and divides the
egg cell, which before division becomes decidedly elongated,
into two nearly equal cells. Ordinarily in each of these cells

Fig. 29. — Spharocarp^MS terrestris var. Cali/omicus (Aust.). Development of the archegonium.
A-C, Longitudinal sections, X 600 ; D, X 300.

similar transverse walls are formed before any vertical walls
appear, so that the embryo consists of a simple row of cells.
As in the Marchantiaceae the first wall separates the future
capsule from the stalk, and in this respect Sphcerocarpus
approaches the Marchantiaceae rather than the Junger-
manniaceae. Following the transverse wajls there are formed
in all the upper cells nearly median vertical ones, which are
intersected by similar ones at right angles to them, so that in
most cases (although this is not absolutely constant) the upper

* Leitgeb (7), vol. iv. p. 68.

THE JUNGERMANNIACE^

half of the young sporogonium at this stage (Fig. 30, A)
consists of two tiers, each consisting of four cells. The lower
part of the embryo is pointed, and the basal cell either under-

Fig. 30. — Sphitrocarpus terrestris var. Califomicus. A, B, Median longitudinal sections of the
archegonium venter, Math enclosed embryos, X 360 ; C, an older sporogonium in median section,
X 360 ; D, a still later stage, showing the large space between the archesporial cells and the wall,
X85.

goes no further division or divides but once by a transverse
wall, and remains perfectly recognisable in the later stages
(Fig. 30, B, C). The other cells of the lower half divide much

78 MOSSES AND FERNS chap.

like those of the upper half, but the divisions are somewhat
less regular.

There next arise in all the cells of the upper half
periclinal walls, which at once separate the wall of the
capsule from the archesporium. This wall in the later stages
(Fig. 30, C, D) is very definite, and remains but one cell thick
up to the time the sporogonium is mature. The further
divisions in the capsule are without any apparent order, and
result in a perfectly globular body composed of an outer layer
of cells enclosing the archesporium, which consists of entirely
similar cells with rather small nuclei and dense contents.
While these changes are going on in the capsule, the lower
part of the embryo loses its originally pointed form, and the
bottom swells out into a bulb (the foot), which shows plainly
at its base the original basal cell of the young embryo. This
bulb is characterised by the size of the cells, which are also
more transparent than those of the other parts of the embryo.

Owing to the development of the stalk of the archegonium,
after fertilisation the whole embryo remains raised above the
level of the thallus, instead of penetrating into it, as is usually
the case. The stalk or portion between the capsule and foot
remains short, and in longitudinal section shows about four
rows of cells. As the calyptra grows the upper part becomes
divided into two layers, the part surrounding the foot into
three. Instead of breaking through the calyptra at maturity,
the capsule grows faster than the calyptra long before it is
mature, and the upper part of the calyptra is first compressed
very much and finally completely broken through by the
enlarging capsule.

Leitgeb^ calls attention to the fact that soon after the
cells of the archesporium begin to separate, the whole mass
of cells becomes completely separated from the wall of the
capsule, which grows rapidly until the cavity within is
much larger than the group of archesporial cells, which thus
float free in the large cavity. Fig. 30, D shows a section
through a sporogonium at this stage. The cells making up
the central mass are apparently alike, but Leitgeb ^ says that
in the living sporogonium part of the cells have abundant
starch and chlorophyll, while in the others these are wanting
or present in much less quantity, while their place is taken by

* Leitgeb (7), vol. iv. p. 70. ^ Leitgeb, Le,

THE JUNGERMANNIACEyE

oil, but that no rule could be made out as to the distribution
of the two sorts of cells. The latter are the spore mother cells,
while the others are gradually used up by the developing
spores. The latter remain united in tetrads, and escape from
the capsule by the gradual decay of its wall and of the sur-
rounding tissue of the gametophyte.

The male plants are very much smaller than the females,
with which they grow and under which they are at times
almost completely hidden. The cell walls of the antheridial
envelopes are often a dark purple-red colour, and this makes
them much harder to see than the vivid green of the female ^
plant. The apical growth and origin of the antheridium is )

Fig. 'ix.—Spharocarpus terrestris var. Califomicus. Development of the antheridium. A-D,
Median longitudinal sections, X450; £, an older one, Xzas; F', a s[>ermatozoid, killed with
osmic acid, x 900.

the same as in Riccia. The first division in the primary
antheridial cell is the same as in that of the archegonium, but
the basal cell is smaller, and does not divide again transversely,
and takes but little part in the formation of the stalk. In the
antheridium mother cell are next formed two transverse walls,
dividing it into three superimposed cells. The two. uppermost
divide, as in the Marchantiaceae, by vertical median walls into
regular octants, the lower by a series of transverse walls into
the stalk, which consists of a single row of cells sunk below the
level of the thallus. After the division of the body of the
antheridium into the octant cells^ periclinal walls are formed
in each of these, so that the body of the antheridium consists
of eight central cells and eight peripheral ones, and the stalk

8o MOSSES AND FERNS chap.

of two cells, of which the upper one forms the base of the
antheridium body (Fig. 31, D). At this stage and the one
preceding it Sphcerocarpus recalls very forcibly the structure of
the antheridium of the Characeae, although the succession of
walls is not exactly the same. The divisions of the central
cells are extremely regular, walls being formed at right angles,
so that the sperm cells are almost perfectly cubical, and the
limits of the primary central cells are recognisable for a long
time.

The development of the antheridial envelope begins much
earlier than that about the archegonium, but in exactly the
same way. By the time that the wall of the antheridium is
formed the envelope has already grown up above its summit,
and as the antheridium develops it extends far beyond it like
a flask, at the bottom of which the antheridium is placed, and
through whose neck the spermatozoids escape. These are
very much like those of the other Hepaticae, and in size exceed
those of most of the Marchantiaceae, but are smaller than is
usual among the Jungermanniaceae.

Leitgeb^ studied the germination of the spores, which
remain united in tetrads permanently. He found that all the
spores of a tetrad were capable of normal development, which
does not differ from that of Riccia or other thalLose Liverworts. ^
A more or less conspicuous gernr tube is found at the end of
which the young plant develops, one of the octants of the
original terminal group of cells becoming, apparently, the
apical cell for the young plant. The latter rapidly grows in
breadth and soon assumes all the characters of the older plant.
Leitgeb (Fig. 17, PI. IX.) shows a condition that looks as if at
an earlier stage a two-sided apical cell had been present, but
he says nothing in regard to this. The sexual organs appear
while the plant is extremely small. Leitgeb says he observed
the first indications of them on individuals only one millimetre
in diameter, and before the first papillate hair on the ventral
surface had been formed.

Corresponding closely in the origin and structure of the
sexual organs to Spharocarpus^ but differing much in habit, is
the peculiar genus RiellUy containing seven species, all sub-
mersed aquatics, and, so far as is yet known, confined to
Northern Africa and Southern Europe. The plant (Fig. 32,
1 Leitgeb (7), vol. iv. PI. IX. Fig. 17.

THE JUNGERMANNIACEj!E

A) grows upright in the water, and consists of a central axis,
about which a membranous expansion winds like the thread
of a screw. Leitgeb ^ has carefully investigated the develop-

Fic y2.—Ruiia helico^kylla (Mont.). A, A female plant enlai^ed ; 9 » sporogonia ; B, lateral,
C, vential view of the growing point, X6oo ; x, the apical cell ; L, leaves (after LeitgebX

ment of the thallus in R. helicophylla and R. Parisii, and found
that the apical growth is like that of Sphcerocarpus^ and that

* Leitgeb (7), vol. iv. p. 74,
G

82 MOSSES AND FERNS chap.

the peculiar wing is a dorsal growth (Fig. 32, B, C). Lateral
leaf- like appendages are developed on either side of the
growing point (Fig. 32, B, C). Both archegonia and antheridia
resemble those of Sphcerocarpus very closely, and the structure
of the capsule is also the same, no true elaters being developed,
but instead these are simply sterile cells. Goebel ^ has
recently made some further investigations upon the develop-
ment of Riella^ and believes that the origin of the growing
point is secondary. His view is, however, based upon a study
of secondary growths from the young thallus, as he was unable
to procure very young germ plants.^

Amur a {Riccardia) and Metzgeria represent the simplest
of the typical anacrogynous Jungermanniaceae. In the former
the thallus is composed of absolutely similar cells, all chloro-
phyll-bearing, and in each cell one or more oil bodies, like
those of the Marchantiaceae. In Metzgeria (Fig. 33) the wings
of the thallus are but one cell thick, and there is a very definite
midrib, usually four cells thick. The apical growth in both
genera is the same, and is effected by the growth of a " two-
sided " apical cell.^ The segmentation is very regular, especially
in Metzgeria (Fig. 33), where each of the segments divides
first into an inner and an outer cell, the former by subsequent
divisions parallel to the surface of the thallus producing the
thickened midrib, the outer cells dividing only by perpendic-
ular walls, forming the wings. From the ventral surface of the
young midrib papillae project, which curve up over the grow-
ing point, in the form of short two-celled hairs, whose end cells
secrete mucilage for its protection. In Aneura the growth is
very similar, but all of the cells divide by walls parallel to
the surface of the thallus, and no midrib is formed, and the
thallus is several cells thick in all parts. In both genera
numerous delicate colourless root-hairs are developed from
th^ ventral surface, especially of the midrib, when that is present.
/^ Aneura is of interest as showing the only case among
/the Bryophytes of structures that may be compared to the
^ zoospores of the green Algae. In A, multifida Goebel * dis-

^ Goebel (14).

' On the fertilisation of the archegonium oi Riella^ see Knich (i).

' "Two-sided" is hardly a strict equivalent for the German "zweischneidig,"
but will be used here in the same sense, ue, an apical cell from which two sets of
lateral see^ments are cut off.

* Goebel (8), p. 337-

THE JUNGERMANNIACEjE

covered that the two-celled gemmae which had been described
as formed simply by a separation of the cells of the thallus,
were really formed within the cells and expelled from them
through an opening, after which they divided into two cells
and ultimately developed a young plant, much as an ordinary
spore would do. The absence of cilia from these cells, which
probably are . the last reminiscences of the ciliated gonidia of

Fig. yi.—Metzgeria pubescens (Radd.). A, Surface view of the thallus in process of division, X 80 ; B,
growing point of a branch showing the two-sided apical cell (jr) and the ventral hairs (A), X 240 ;
C, the growing point in process of division, jt, -r', the apical cells of the two brapches, X 480.

the aquatic ancestral forms, is to be accounted for by the
terrestrial habit of Aneura.

The branching is dichotomous, and is brought about by
the formation of a second apical cell in one of the youngest
segments. This apical cell is formed by a curved wall, which
strikes the outer wall of the segment (Fig. 33, C). Thus
two apical cells arise close together, and as segments are cut
off from each, they are forced farther and farther apart, and

MOSSES AND FERNS

CHAP.

serve as the growing point of two shoots, which may continue
to grow equally, when the thallus shows a marked forking
{M. furcatd), or one of the branches grows more strongly than
the other, which is thus forced to one side and appears like a
lateral branch {A, pinnatifida. Fig. 38, B).

The sexual organs in both Amur a and Metzgeria are borne
on short branches, which in the latter arise as ventral structures,

Fig. 34. — Aneura pinnaH/lda (Nees).^ A, Part of a thallus with two antherldial branches, slightly
magnified ; B, an archegonial branch, X 40 ; C, cells from the margin of the archegonial branch
showing the oil bodies {p\ x 300.

but in Aneura are simply ordinary branches that are checked
in their growth by the production of the sexual organs, and
not infrequently may grow out into ordinary branches after the
formation of the sexual organs has ceased. In A. pinnatifida
(Fig 34, B) archegonia and antheridia are usually produced
upon separate branches, but may occur together.

The origin of the antheridia can be readily followed in sections

THE JUNGERMANNIACEJE

made parallel to the surface of a male branch. The apex is
occupied by an apical cell of the usual form, and the cell divisions
in the young segment are extremely regular. The segment first
divides into an inner and an outer cell, and the former probably
next into a dorsal and a ventral one. The dorsal cell divides
by a longitudinal wall into two nearly equal cells, of which the
inner one, dividing by a wall perpendicular to the first, gives
rise to the primary cell of the antheridium (Fig. 35, A<?).
This cell now projects above the surface of the thallus, and

Fig. 35. — Antura pinnatifida (Nees). A, Horizontal section of the ap)ex of a young antheridial branch,
X 565 ; jr, the apical cell ; ^ , antberidia ; B, transverse section of a young archegonial branch,
passing through the apical cell (^) ; 9 > young archeg^nia, X 525 ; C, longitudinal section of a
nearly ri[>e archegonium, X26a; D, £, spennatozoids of Peiiia caiycina^ X1225 (D, £, after
GuignardX

divides into a single stalk cell, which undergoes no further
divisions, and the antheridium mother cell. The divisions in the
latter correspond to those in the other Jungermanniaceae. First
a vertical wall is formed, dividing the young antheridium into
two equal parts. Next, in each of these, two walls arise, inter-
secting each other as well as the median wall, and dividing
each half of the antheridium into three cells, two peripheral
ones and a central one. (A somewhat later stage than this is
shown in Fig. 35, A.) The peripheral cells do not reach to

86 MOSSES AND FERNS chap.

the top of the antheridium, and next a periclinal wall is formed
near the top of the central cells, by which a third peripheral
cell is formed in each half of the antheridium, which now con-
sists of two central cells and six peripheral ones. The further
divisions were not followed in detail, but seem to correspond
with those in the higher forms.

Of the two first cells into which the dorsal cell divides, the
one which does not produce the antheridium, together with the
inner of the two into which that cell first divides, form a
partition which rapidly increases in height with the growth
of the antheridia, and separates each from its neighbour
by a single layer of cells, so that the antheridia are sunk
in chambers, arranged in two rows, corresponding to the two
series of segments of the apical cell.

The archegonia are borne upon similar but shorter branches,
and here too the development is very regular. In Fig. 35, B,
a vertical section through the end of a young female branch is
shown with the apical cell {x). Segments are here, too, cut off
alternately right and left, and from each segment an arche-
gonium develops. The segment is first divided, probably, as
in the male branch and the vegetative ones, into an inner and
an outer cell, but I did not succeed in getting satisfactory longi-
tudinal sections parallel to the surface, so cannot speak posi-
tively on this point. The youngest segment, in which the
archegonium mother cell is recognisable, shows in vertical sec-
tion three cells, a small ventral one, a middle larger one, and
a dorsal one — the archegonium mother cell. The latter does
not form any stalk, but divides at once by the three intersect-
ing walls, as in other Hepaticae, and the further development
corresponds with these, except that the base of the arche-
gonium is not free, and the central cell is below the level of
the superficial cells of the thallus. The archegonium neck is
short, and the basal part as well as that part of the venter
which is free, two cells thick (Fig. 35, C). The number of
neck cells is small (apparently about four), but whether the
number is constant cannot be stated positively. The female
branch remains very short, and the archegonia, which are only
produced in small numbers (usually not more than six to eight),are
close together and surrounded by an irregular sort of envelope
formed by the more or less incurved and very much laciniated
margins of the branch. Secondary hair-like growths are also

THE JUNGERMANNIACE^

formed, so that to the naked eye the archegonial receptacles
appear as densely fringed and flattened tufts upon the sides of
the larger branches.

The earliest stages in the embryo are not perfectly known.
Kienitz-Gerloff^ investigated Metzgeria furcata and Leitgeb^
species of Aneura. In both of these the first division in the
embryo separates an upper cell, from which capsule and seta
develop, from a lower cell, which forms a more or less conspicu-
ous appendage at the base of the foot. The earliest divisions
in the upper part are not known, but it soon becomes a cylindri-
cal body consisting of several tiers of cells, each composed of

A C

■ B

Fig. 36. — A, Young embryo of Antura muitt/lda (Dum.\ optical section, Xa33 (after Leitgeb);\B,
median longitudinal section of an older sporogonium of ^. ^ingyttf (Dum.), X35 ; C, upper part of
B, X aoc ; s/, sporogenous celb ; #^ young elaters ; m, aincal group of sterile cells.

four equal quadrant cells. According to Leitgeb,^ the upper
tier, from which the capsule develops, is formed by the first
transverse wall in the upper part of the embryo. This upper
tier is next divided by nearly transverse walls into four terminal
cover cells, and four larger ones below, and these latter are again
divided each into three cells, an inner one and two outer ones,
so that the capsule consists of four central cells, the arche-
sporium, and twelve wall cells (Fig. 36, A). A similar division
in the lower tiers results in the formation of four axial rows
and a single outside layer of cells in the stalk. In the
lowest tiers the divisions are much less regular, and the first,

1 Kienitz-Gerloff(i).

* Leitgeb (7), vol. iii. p. 47.

' Leitgeb, /.c.

MOSSES AND FERNS

CHAP.

which is not very largely developed, shows no definite arrange-
ment of the cells. The part of the wall of the capsule formed
from the four cover cells later become two-layered, but the rest
remains but one cell thick. In Metzgeria^ the wall becomes

later two - layered. The
archesporium divides first
into two layers. In the
upper cells the divisions
are more regular than in
the lower one, and later
the archesporium is made
up of cells arranged in
more or less regular lines,
starting from just below
the apex and radiating
from this point, extending
to the base of the capsule.
These cells are at first of
similar form, and with the
growth of the capsule
become elongated with
pointed ends that fit to-
gether without any spaces
between. Some of these
cells, however, divide
rapidly by transverse walls
and give rise to rows of
isodiametric cells (Fig. 36,
sp\ wedged in between
others that have remained
undivided {el). The former
are the young sporogenous
cells, the latter the elaters.
A mass of cells lying just
below the apex, and be-
longing to the archesporium, remains but little changed, and
forms the point of attachment for the elaters after the capsule
opens (Fig. 36, B, C, tn).

The further development of spores and elaters is similar to
that in the higher Marchantiaceae, and when the capsule is

^ Leitgeb (7), vol. iii. PI. II. Fig. 9.

Fig. yj.—Fosiombronia longiuta (AustX A, Section
through a young tetrad of spores ; B, surface view
of the wall of a young spore ; C, two young elaters,
X6oo ; D, two ripe spores ; E, elater, x 300.

IV THE JUNGERMANNIACE^ 89

mature it opens by four valves which extend its whole
length.

The germination of the spores of Aneura has been studied
by Kny^ in A. pcdmatdy and by Leitgeb^ in A, pinguisy which
agrees in all respects with the former. The spores, as is usual
in the Jungermanniaceae, have a poorly -developed exospore,
and contain chlorophyll when ripe. Before any divisions take
place, the spore enlarges to two or three times its original
volume, and then elongates and by repeated cross-walls forms
a filament of varying length. In the end cell next an inclined
wall arises, which is met by another nearly at right angles to it,
and thus the two-sided apical cell is established, and the thallus
gradually assumes its complete form (Fig. 40, A).

In the other thallose anacrogynous forms, i.e. Pallavidnia
(Fig. 38, A), the sexual organs are borne upon the dorsal
surface of the ordinary shoots, usually surrounded by a sort of
involucre. In most of these forms the apical cell is of a
different type from that of Aneura^ but is variable even in the
same species. Thus in Pallavicinia cylindrical while the
commoner form is nearly wedge-shaped, appearing four-sided
seen from the surface, and triangular in vertical section, it may
approach very nearly the two-sided type (Fig. 39, C). In the
ordinary form four sets of segments are cut off, — dorsal and
ventral, as in Riccia or SphcsrocarpuSy and two sets of lateral
ones. In Pellia ccUycina the apical cell shows a similar form,
but in P, epiphylla (Fig. 39, D, E) another type is seen.
Here, while the surface view is the same as in P. ccUycina^
in vertical section the cell is nearly semicircular, i£, here
there are but three sets of segments, two lateral ones and a
basal one extending the whole depth of the thallus, and only
later showing a division into ventral and dorsal cells. Probably
this type has been derived from the former by a gradual in-
crease in the size of the angle formed by the dorsal and ventral
walls of the apical cell, which finally became so great as to
practically form one plane.

Janczewski ^ followed very carefully the development of the
archegonium in Pellia epiphyllay which differs a good deal from
that of Aneura, The archegonia are formed in groups just
back of the apex, but he does not seem to have been able to
detect any relation between them and the segments of the

* Kny (1). ' Leitgeb (7), vol. iii. p. 48. ^ Janczewski (i), p. 389.

MOSSES AND FERNS

CHAP. IV

apical cell such as obtains in Aneura, but it seems probable
that such a relation does exist. After the archegonium mother
cell is cut off, it does not at once divide by vertical walls, but
there is first cut off a pedicel, after which the upper cell under-

FiG. 38.-- A, PaUavicinia cylindrica (|Aust.)i X4; /rr, the elongated perianth; B, Anenra
/innati/lda (L.), x6; 9« archegonial branches; C-E, Fossombronia longiseta (Aust.), X4; F,

goes the usual divisions. Of the three peripheral cells one is
much smaller and does not as a rule divide longitudinally, so
that the neck has normally but five rows of cells instead of six, as
in the Marchantiaceae. Owing to the formation of the pedicel,

Fio. 39. — A, Vertical, B, C, horizontal sections through the apex of PallavictMia eylindrica (Aust.),
X, apical cell, A, X2a5 ; B, C, X450 ; D, E, Pellia e/iphylia (Nees); D, vertical section ; E,
horizontal (optical) section, X450.

MOSSES AND FERNS

CHAP.

the archegonium is quite free at the base, and like that of
Aneura the wall of the venter is two- layered. The neck
becomes very long, and, according to Janczewski, the number of
neck canal cells may reach sixteen or even eighteen.

The antheridia of Pellia are larger than in Aneura, but in
their development are similar except that the stalk is multi-
cellular. The spermatozoids
are the largest- known among
the Hepaticae (Fig. 35, D, E).
In some species of Palla-
vicinia the very strongly de-
veloped midrib is made up
in part of thick-walled elon-
gated cells, but usually such
cells are absent The develop-
ment of the sporogonium
is best known in Pellia epi-
phylla} Here the first wall,
as in * Aneura, separates a
lower cell, which simply forms
an appendage, from the upper
cell, from which the stalk and
capsule develop. In the
latter the first wall is vertical,
and is followed in each of
the resulting cells by hori-
zontal walls, by which the
separation of the capsule from
the seta is effected. These
four cells are now divided
by vertical walls, so that two
layers of four cells each are
present. The first periclinal
walls in the apical group of cells separate the archesporium
from the wall of the capsule.

The differentiation of the capsule and seta follows as in
Aneura, and the arrangement of the cells of the archesporium is
much the same except that the rows of cells radiate from the
base of the capsule and not from the summit. The foot is
very distinct and forms a pointed conical cap, whose edges
• 1 Kienitz-Gerloff (i) ; Hofmeister (i).

Fig. 40. — A, Young plant of Aneura palmata
(Nees), X 265 (after Leitgeb) ; B. three views of a
young plant of Pellia calycina^ X 490 (LeitgebX

IV THE JUNGERMANNIACE^ 93

overlap the base of the seta. As in Targionia, and this is true
for the other Jungermanniaceae, the spore mother cells become
deeply four-lobed before the division of the nucleus takes place.
Farmer^ has recently studied this carefully in Pcdlavicinia
decipiens and also in species of Aneura. In the former, previous
to the division of the nucleus, there is formed a " quadri-polar
nuclear spindle," which extends into each of the four divisions
or lobes of the cell. Then follows a division of the chromosomes
into four groups, apparently without the daughter nuclei first
assuming the resting stage, and these four groups of chromo-
somes travel to the four poles of the spindle and gradually as-
sume the form of resting nuclei, after which the division walls
are formed, completely dividing the cavity of the cell. The
division of the nucleus occurs very late here, sometimes the
thickenings upon the outside of the spores being indicated
before the primary nucleus divides. In Aneura multifida, the
formation of the quadri-polar spindle occurs, but there is after-
ward a formation of two distinct nuclear figures of the ordinary
type.

The growth of the seta after the spores are ripe is ex-
tremely rapid, but consists entirely in a simple elongation of the
cells. Askenasi ^ has investigated this in Pellia epiphylla^ and
states that in three to four days the seta increases in length fron)
about I mm. to in some cases as much as 80 mm., and that this
extraordinary extension is at the expense of the starch which
the outer cells of the young seta contain in great abundance,
but which disappears completely during the elongation of the
seta. The growing sporogonium here as well as in other
species is strongly heliotropic.

The calyptra in the thallose Anacrogynae is usually massive,
and in addition there is formed about the growing sporogonium
a special envelope inside the involucre, which in Pallavtctnia
especially (Fig. 38, A) becomes prolonged into a tube which
completely encloses the sporogonium until just before its
dehiscence.

The further development of the spores and elaters corre-
sponds with that of the Marchantiaceae (Fig. 37), and here there
is the same method of the development of the thickenings
upon the walls of the elaters and the spores. In cases where
the spores germinate immediately, chlorophyll is developed and

^ Farmer (4). ^ Askenasi (i).

94 MOSSES AND FERNS chap.

no proper exospore is formed, although the outer layer of the
cell wall is more or less cuticularised.

In the germination of the spores Pellia offers an exception
to the other Jungermanniaceae, in that the spores divide into
a multicellular body before they are discharged from the capsule*.
The presence of centrospheres in the dividing nuclei has been
recently demonstrated by Farmer.^ The ripe spore here is an
oval body which consists of several tiers of cells, the end cells
being usually undivided, and the middle ones each consisting of
four equal quadrant cells. There is some disagreement as to
the earliest stages in the germination and the establishment of
the apical growth.^ Hofmeister ^ states that in P, epiphylla one
end cell of the spore grows out into the first rhizoid, wHile the
other develops into the growing point of the young plant.
Miiller,* on the other hand, states that in P, ccUycina both ends
of the spore develop root-hairs while the growing point, which
at first has a two-sided apical cell, like that of Metzgeria^ arises
laterally.

Connecting the strictly thallose anacrogynous Hepaticae
with the foliose acrogynous ones, are a number of most in-
structive intermediate forms. Of these Blasia (Fig. 38, F) is
perhaps the simplest. Here the margin of the thallus is lobed,
and these lobes, according to Leitgeb's ^ view, are very simple
leaves. In Fossombronia (Fig. 38, C, D), while the general
thallose form is more or less evident, the leaves are unmistak-
able, and as their development shows, morphologically the same
as the leaves of the acrogynous forms. The most remarkable
form, however, is Treubia insignis^ a very large foliose Liverwort
discovered by Goebel in Java. This has all the appearance
of a very large acrogynous form, and also the typical three-
sided apical cell ; but in regard to the position of the sexual
organs it is typically anacrogynous. These and the Haplo-
mitrieae form a perfect transition from the Anacrogynae to the
Acrogynae.

The multicellular gemmae of Blasia ^ have been alluded to.
These are produced in long flask-shaped receptacles, and when
mature form nearly globular brownish bodies whose cells contain
much oil, and whose stalk consists of a simple row of cells.
Among these are glandular hairs, which secrete mucilage, by the

1 Farmer (5). ^ Hofmeister (i), p. 21. » MUller, N. J. C. (i), p. 257.
* Leitgeb (7), vol. i. p. 5. ® Leitgeb, l.c, p. 58.

IV THE JUNGERMANNIACE^ 95

swelling of which the gemmae are loosened from their pedicels,
as in Marchantia. Similar but simpler gemmae having usually
three cells occur in Treubia} Blasia is also characterised by
the presence of colonies of Nostoc within the thallus. These
occupy cavities in the bases of the leaves and are normally
always present

The HaplomitriecB

The two genera, Haplomitrium and Calobryum, which consti-
tute this family, differ from all other Hepaticae in having the
leaves radially arranged, and not showing the dorsiventral form
that characterises all the others. The plants are completely
destitute of rhizoids but possess a rhizome-like basal part, from
which the leafy axes arise. The latter have well -developed
leaves arranged more or less distinctly in three rows. The
stem grows from a tetrahedral apical cell, as in the acrogynous
forms, but in Haplomitrium at least the apical cell does not
develop into an archegonium. The archegonia are in this
genus borne at the end of ordinary shoots, but in Calobryum
the end of the female branch becomes much broadened and the
numerous archegonia stand crowded together. In this case it
is possible that the apical cell of the stem may finally produce
an archegonium. Much the same difference is observable in
the arrangement of the antheridia.

Classification

Jungermanniaceae Anacrogynae. Apical cell of female axis
never becoming transformed into an archegonium.

A. Anelatereae. No true elaters, but sterile cells repre-
senting these. Capsule cleistocarpous. Here belong
the three genera, Thallocarpus^ Spkcerocarpus^ Riella.

B. Elatereae. Capsule opening either by four valves or
irregularly. Elaters always developed.

a. Gametophore always dorsiventral, either strictly thallose
or with more or less developed leaves. Families, —
Metzgerieae, Leptotheceae, Codonieae.

b. Gametophore upright with three/ rows of radially
arranged leaves. Fam. I., Haplomitrieae.

1 Goebel (13).

MOSSES AND FERNS

CHAP.

The HepaticcB Acrogynce

Treubia and Haplomitrium^ as we have seen, connect almost
insensibly the anacrogynous with the acrogynous Hepaticae.
The latter are much more numerous than the former, but much
more constant in form, and are doubtless a later specialised
group derived from the former. While differing in the form
and arrangement of the leaves and other minor details, they
are remarkably constant in their method of growth and in the
position of the sexual organs, especially the archegonia. These
are always formed upon special branches, where, after a varying

number of segments are
cut off, the apical cell
becomes the mother cell
of an archegonium. The
study of any typical form
will illustrate the prin-
cipal characters of the
group. The species
selected, Porella {Mado-
theca) Bolanderi^ is very
like the common and
, -^ widely distributed P.
platyphylla, which corre-
sponds with it in all
structural points.

The plant grows

¥iG. ^x,-P0rellaBoland€H(,\xisU). A, Female plant, X 4 ;• upon rOCks, especially,
9, archegonial branches; B, an open sporogonium, * \ \

X4; C, a male plant, X4; <J, the antheridial branches, but alsO Upon the trUnkS

of trees, and forms dense
mats closely covering the substratum. It branches extensively,
but always monopodially, dichotomous branching never occurring
in the acrogynous Jungermanniaceae. The slender stem is com-
pletely hidden above by the two rows of closely-set, overlapping,
scale-like leaves. Upon the ventral side, which is fastened by
scattering rhizoids to the substratum, there is a rmv of much
smaller leaves (Amphigastria), more or less irregularly disposed.
The dorsal leaves are nearly oval in outline, but the two-
lobed form, that is very conspicuous in many species, is not so
noticeable here. The amphigastria are much smaller, and more
elongated than the dorsal leaves. The structure of the leaf is

THE JVNGERMANNIACE^

of the simplest character, consisting of a single layer of polygonal
cells containing numerous chloroplasts.

The plants grow where they are exposed to alternate
wetting and drying up. They may at any stage become
completely dried up, and bn being moistened will resume at
once their activity. In the dried condition, the species under
consideration often remains for several months without

Fic. 42.— Poreiia BoiatuUri (Aust.). A, Median longitudinal section of a vegetative axis ; B, a
cross-section of the apex of a similar one, x 500 ; j-, the apical cell ; A, hair ; d^ dorsal surface^;
r, ventral surface. ^

apparently being injured in the least, and this power is shared
to a considerable degree by most of the acrogynous forms, whose
favourite habitat is the trunks of trees.

The apical growth of the stem is extremely regular, and as in
all the other acrogynous Hepaticaa, the apical cell is a three-sided
pyramid (Fig. 42, A). In longitudinal section it is much deeper
than broad, and its outer face is almost flat In cross-sections
(Fig. 42, B) it has the form of an isosceles triangle, the shorter

98 MOSSES AND FERNS , ^k[) chap.

side turned toward the ventral surface of the plant. From this
cell three sets of lateral segments are cut off, two dorsal and
one ventral, and each of these gives rise to a row of leaves, a
leaf corresponding to each segment of the apical cell. The
first division wall in each segment is at right angles to its
broad faces and divides it into two cells of somewhat unequal
size. The next wall formed divides the larger of the two
primary cells into an inner and an outer cell {Fig. 42, A), so that
the young segment now consists of three cells, an inner one
and two outer ; the latter in the dorsal segments correspond to
the two lobes usually found in the dorsal leaves. The two outer
cells now divide by walls in two planes, and rapidly grow out
above the level of the apical cell and form lamellae which re-
main single-layered, and undergo but little further modification
beyond an increase in size. From the base of the young leaves
simple hairs develop, but remain small and inconspicuous. The
inner of the three first formed cells of the segment, by further
division and growth in all directions, produces the axis of the
plant. This in cross or longitudinal section shows almost
perfectly uniform tissue. No distinct epidermis, or central
strand, like that found in most Mosses, can be seen.

The branching is monopodial and the branch represents
the ventral lobe of a leaf. After the first division by which
the two lobes of the leaf are separated, only the dorsal one
develops into the lamina of the leaf, which is thus in the
segment from which a branch is to form, only one-lobed. In
the ventral cell three walls arise (Fig. 43), intersecting so as
to cut out a pyramidal cell of the same form as the apical cell
of the main axis, and the cell so formed at once begins to
divide in the same way, and forms a lateral axis of precisely
the same structure as the main one.

The plants are strictly dioecious and the two sexes are at
once recognisable. The males are smaller, and bear special
lateral branches which project nearly at right angles from the
main axis, and whose closely imbricated light green leaves
make them conspicuous. At the base of each of the leaves is
a long-stalked antheridium, large enough to be readily seen
with the naked eye.

The development of the antheridium may be easily traced
by means of sections made parallel to the surface of the
branch. At the apex (Fig. 42, C) is an apical cell nnich

IV THE JUNGERMANNIACE.^ 99

like that in the sterile branches, but with the outer face
more convex. The divisions in the segments are the same
as there, but the whole branch remains more slender,
and the hairs at the base of the leaves are absent The
antheridia arise singly from the bases of the leaves, close to
where they join the stem, and are recognisable in the fourth or
§fth youngest leaf (Fig. 42, C, i ). The antheridia! cell
assumes a papillate form, and divides by a transverse wall into
an outer and inner cell, and the foroiet^ divides by a similar
wall into two cells, of which the upper one is the mother cell

Fig. 43. — Diagram showing the ordinary method of branching in the acrogynous Jungermanniacese
(after Leitgeb). D, Dorsal ; V, ventral part of stem ; X' X", apical cells of the branches. The
segments are numbered.

of the antheridium, and the other the stalk. The first wall in
the antheridium itself is vertical (Fig. 44, B), and divides it
into two equal parts. Each of these is now divided by two
other intersecting walls, best seen in cross-section (Fig. 45, A),
which separate a central cell, nearly tetrahedral in form, from
two outer cells. In the complete separation of the central
cell by these first two walls, Porella appears to differ from the
other Jungermanniacese examined,^ where these first two
peripheral cells do not reach to the top of the antheridium,
^ Leitgeb (7), vol. ii. p. 44.

lOO

MOSSES AND FERNS

CHAP.

and a third cell is cut off before the separation of the central
part of the antheridium from the wall is complete. It is
possible, too, that in Porella this may be sometimes the case.
The antheridium in cross-section at this stage shows two
perfectly symmetrical halves (Fig. 45, A). The two central
cells form a rhomboid surrounded by six cells, the first of the
primary peripheral cells being in each case divided into twof
The divisions proceed rapidly in both the central cells and in
the peripheral ones. In the latter they are for a long time

Fig. ^^.— Porella Bolanderi (Aujt). Successive stages of the young antheridium in nv^ian
longitudinal section, x6oc.

always radial, so that the wall remains but one cell thick ; but
as the antheridium approaches maturity periclinal walls also
form in the lower part, which thus becomes * double, and at
points even three cells thick. After the division of each
primary central cell into equal quadrants, a series of curved
walls intersecting the inner walls of the peripheral cells arise,
and then periclinal walls (Fig. 45, C), but beyond this no
definite succession of walls could be traced.

The development of the spermatozoids is the same as in other
Liverworts. The slender body shows about two complete coils ;

THE JUSGERMANNIACE^

lOI

the vesicle is small, but always present, and the cilia somewhat
longer than the body (Fig. 45, F). The stalk of the antheridium
is long and at maturity composed of two rows of cells. Before
the central cells of the antheridium are separated from the peri-
pheral ones, the stalk shows a division into two tiers of two
cells each (Fig. 44, B), but it is only the lower one that forms
the real stalk ; the other forms the base of the antheridium
itself. The cells of the wall have numerous chloroplasts, but
the great mass of colourless sperm cells within make the ripe

Fig. 45. — Porella Bolanieri (Aust.). A, B, Cross-sections of young aniheridia, X6oo; C, longi-
tudinal section of nearly ripe antheridium, X loo ; D, ripe antheridium in the act of opening,
X 50 ; £, F, spermato/oids, X 1200.

antheridium look almost pure white. If one of these is brought
into water it soon opens in a very characteristic way. The
cells of the wall absorb water with great avidity, and finally
the upper part bursts open by a number of irregular lobes
which curl back so strongly that many of the marginal cells
become completely detached. The whole mass of sperm cells,
with the included spermatozoids, is forced out into the water,
and if they are perfectly mature, the spermatozoids are quickly
liberated and swim away (Fig. 45, D).

The female plants are decidedly larger than the males, but

I02 MOSSES AND FERNS chap.

the archegonial branches are much less conspicuous than the
antheridial ones. The older ones, which either contain a young
sporogonium or abortive archegonia, are readily distinguished
on account of the large perianth (Fig. 41, A), but those that
contain the young archegonia are situated very near the apex
of the main shoot, and are scarcely to be distinguished from
the very young vegetative branches. However, a plant with
the older perichaetia, or very young sporogonia, will usually
show young archegonial branches as well.

The archegonial branch originates in the same way as the
vegetative branches, and the first divisions of its apical cell are
the same ; but only two or three segments develop leaves,
after which each young segment divides into an inner and
an outer cell ; the latter becomes at once the mother cell of
the young archegonium. The inner cell divides further by a
transverse wall, and the outer of the two cells thus formed gives
rise to the short but evident pedicel of the archegonium. The
latter is very like that of the anacrogynous Liverworts. Of the
three first walls (Fig. 46, C), the last formed one is much
shorter, so that one of the three peripheral cells is much
smaller, and does not divide by a vertical wall, and the neck
has but five rows of cells, as in Pellia. This appears to be
universal among the Jungermanniaceae examined.^ Often in
Porella the three primary walls converge at the bottom so as
to almost, meet, in which case the central row of cells is
narrower at the base (Fig. 46, D). The rest of the develop-
ment is exactly as in the other Hepaticae. The number of
neck canal cells in the full-grown archegonium is normally
eight. The archegonium (Fig. 46, L) at maturity is nearly
cylindrical, with the venter but little enlarged. The canal cells
are broad, but the egg small. The venter has a two-layered wall.

The first-formed archegonia arise in strictly acropetal
succession, and finally the apical cell divides by a transverse
wall, and the outer cell so formed becomes transformed into an
archegonium. In a number of cases observed, young arche-
gonia were noticed among the older ones, apparently formed
secondarily from superficial cells between them, and not from
the younger segments of the apical cells.

A perianth is formed about the group of archegonia, much
as in the anacrogynous forms.

^ Janczewski (i), p. 393.

THE JUNGERMANNIACE^

103

The early divisions in the embryo of Porella are less regular
than those in some others of the foliose Liverworts. The
embryo at first is composed of a row of cells, of which the
lowest, cut off by the first transverse wall, undergoes here
no further development. In Jungermannia bicuspidata ^ this
lower cell undergoes further divisions to form the filamentous
appendage at the base of the sporogonium. The next divisions

Fig. 46. — Porella Bolanderi (A.ust.X Development of the archegonium, x6oo; C, cross-section of
young arcfaegonium ; G, cross-section of the neck of an older one. The others are longitudinal
sections ; b^ ventral canal cell ; <?, the egg. •

in the upper part of the embryo correspond closely to those
described in Pellia and Aneura, but the succession of the walls
is more variable and the limits of the primary cells more
difficult to follow. The number of the cells, too, that contribute
to the formation of the capsule, cannot be determined exactly,
and there is evidently some variation in this respect, as there
is in the time of the separation of the capsule wall from the

^ Leitgeb, Hofmeister, Kienitz-Gerloff.

I04

MOSSES AND FERNS

archesporium. Both longitudinal and transverse sections of
the sporogonium at this stage (Fig. 47) show a good deal of
irregularity in the arrangement of the cells, and the first
periclinal walls form at very different distances from the
surface, so that it is clear that the wall cannot be established,
as in Radula for instance, by the first periclinals.

The cells of the older archesporium are arranged in more or
less evident rows radiating from the base (Fig. 48, A). No
definite relation of spores and elaters can be made out, the two
sorts of cells being mingled apparently without any regular order.
Some of the cells cease dividing and grow regularly in all direc-

FiG. ^T.— Partita Bolanderi (Aust.). Development of the embryo. A-D, in longitudbal section ;
E-G, transverse sections. B and C are sections of the same embryo, and E, F, G are
successive sections of a single embryo, X 525.

tions, while others may divide further and grow mainly in the
plane of division, so that they become elongated. The former
are the young spore mother cells, the latter the elaters (Fig. 48,
C). The division of the spores begins while the cells of the
archesporium are still united, although at this time the swollen
and strongly striated cell walls of the mother cells (Fig. 48, C)
show that they are becoming mucilaginous. At this stage
sections through the archesporium show the deeply -lobed
spore mother cells with the elongated elaters packed in between
them, the pointed ends of the latter fitting into the interstices
between the spore mother cells. The latter are somewhat
angular and the wall distinctly striated. It is the inner layer

THE JUNGERMANNIACE^

105

only of the wall that projects into the cavity of the cell and
forms the characteristic lobes marking the position of the

Fig. 48. — Porella lioiatuieri (\\\%i.). A, Nearly median longitudinal section of an advanced embryo,
X 360 ; B, the upper part of a similar embryo, X 535 ; C, sporogenous cells and elaters from a
still older sporogonium, X 535.

four spores. The cell cavity is filled with crowded granules,
some of which are chloroplasts. The nucleus, which is of

io6

MOSSES AND FERNS

CHAP.

moderate size, and rich in chromatin, has a distinct nucleolus.
The elaters have thinner walls than the spore mother cells, and
the contents are more finely granular. A distinct nucleus
staining strongly with the usual reagents is present. The
further history of spores and elaters corresponds closely with

that of the forms already described.
The ripe spores have only a thin
wall, which is coloured brown, and
has delicate granular thickenings.

In a paper by Le Clerc du
Sablon ^ the statement is made, and
figures are given, showing that at an
early stage in the development of
the spores and elaters of a number
of Hepaticae the walls of the cells
are completely destroyed, so that
the young spore mother cells and
elaters are primordial cells. A
great many carefully stained micro-
tome sections of a large number of
Liverworts belonging to all the
principal groups have been examined
by me, and invariably the presence
of a definite cell wall can be demon-
strated at all stages.

Many of the foliose Hepaticae
show much greater regularity in the
early divisions of the embryo, and
in the establishment of the arche-
sporium and the arrangement of its
cells. This is especially marked in
Frullania? Here, after the upper

Fig. ^i^.—PortUa Bolanderi (Aust). .r^i- t_ i_ j*»jj«j.

Longitudinal section of a sporo- part of the embryo has divided into
gonium after the final division of the three tiers of cells, these undergo

sporogenous cells, X 85. j ^ j- • • j

the usual quadrant divisions, and
the four terminal cells only, form
the capsule, in which the archesporium is established by
the first periclinal walls (Fig. 50). The divisions in the
archesporium are also extremely regular, so that the spores
and elaters form regularly alternating vertical rows. In

1 Le Clerc du Sablon (3). « Leitgeb (2), vol. ii.

THE JUNGERMANNIACE^

107

Frullania the lower cell of the embryo, instead of remaining
undivided, or forming simply a row of cells, divides repeatedly,
and the cells grow out into papillae, so that it probably is
functional as an absorbent organ, like the foot of the Antho-
ceroteae. Radula^ and Jungermannia^ while more regular in
the divisions than Porella^ still are less so than Frullania, and
in these more than the upper tier of cells take part in the
growth of the capsule. The degree to which the seta and foot
are developed varies. In Porella there is not a distinctly marked
foot, the lower part of the seta being simply somewhat enlarged,
but in others, like Jungermannia bicuspidata, there is a large
heart-shaped foot, very distinct from the seta. In Porella the
seta is short, projecting but little beyond the perianth ; but in
others it may reach a length of several centimetres.

The development of the perianth is quite independent of

Fig. 5a — Frullania dilaiaia (51 ecs). Development of the embryo, X 300 (after Leitgeb) ; x^ x^ the
archesporial cells. The numbers indicate the primary transverse divisions.

fertilisation, and not infrequently it contains, although fully
developed, only abortive archegonia. It is not always formed,
but when present, according to Leitgeb,^ it is the product of the
older segments of the apical cell from which archegonia are
formed, and arises as a sort of wall about the whole group of
archegoniqcyyftjKP^r^//^, as well as most of the foliose Hepaticae,
the capsule^pens by four equal valves, the lines of splitting
corresponding, according to Leitgeb, to the first quadrant walls
in the young embryo.

The germination of the spores shows a great deal of varia-
tion, and has been studied in a large number of forms by
several observers. Recently a number of tropical species have
been investigated, especially by Spruce ^ and Goebel,^ and some
extremely interesting variations have been discovered. In these

* Hofmcister (i). ^ Leitgeb (i), vol. ii. p. 47. ' Spruce (2). "• Goebel (12).

io8 MOSSES AND FERNS chap.

forms when the exospore is not strongly developed, it is simply
stretched by the expanding endospore, and finally becomes no
longer discernible ; but when it is clearly differentiated, it splits
with the swelling of the endospore and then remains unchanged
at the base of the young plant. The germinating spore may
give rise to a cell mass immediately, which develops insensibly
into the leafy axis, or it may form a simple or branched
protonema of very different form, which sometimes reaches
a large size and upon which the leafy axis arises as a bud.

The simplest form may be illustrated by Loplwcolea, Here
the germinating spore divides by a transverse wall into two
equal cells, one of which continues to grow and divide until a
short filament is formed. After a varying number of transverse
divisions an oblique wall is formed in the terminal cell, and a
second one nearly at right angles to it. By these divisions the
dorsiventral character is established, the first-formed segment
being ventral. A third oblique wall now arises, intersecting
both of the others, and the three include a tetrahedral cell
which is the permanent apical cell of the young plant. The
ventral segments do not at first form any trace of leaf-like
structures, and in the dorsal segments the leaves are at first
simple rows of cells ; but a little later the leaves show plainly
their two-lobed character, each being made up of two rows of
cells united at the base. From the ventral segments the
amphigastria develop gradually, being quite absent in the
earlier ones. Chiloscyphus closely resembles Lophocolea^ but the
filamentous protonema is longer, and is often branched. A
similar filamentous protonema is present in Ceplialozia {Junger-
mannid) bicuspidata and other species.

Lejeunia^ shows a most striking resemblance in its early
stages to the simple thalloid Jtingermanniaceae. The germinat-
ing spore forms either a short filament or a cell surface (Fig.
51, A). In either case, at a very early stage, a two-sided apical
cell is established, and for a time the young plant has all the
appearance of a young Metzgeria or Aneura. This two-sided
apical cell gives place to the three-sided one found in the older
gametophyte, and the leaves and stem are gradually developed
as in LopJiocolea,

In Radula^ and according to Goebel, much the same con-
dition occurs in Porella^ the first divisions of the spore give rise
* Goebel (12). '^ Goebel (12) ; Hofmeister (i), p. 55.

IV THE JUNGERMANNIACE^ 109

to a disc, and the formation of a filament is completely sup-
pressed. This disc is nearly circular in outline, and at its edge
a single large cell appears (Fig. 51, B), whose relation to the
primary divisions of the spore is not quite clear. This cell
forms the starting-point for the growing apex of the gameto-
phore. As in the other forms, the first leaves are extremely
rudimentary, and only gradually is the complete gametophyte
developed.

How far this variation in the form of the protonema is of
morphological importance is a question, as the same species
may show both a filamentous protonema and the discoid form.
According to Leitgeb this is the case in several species of
Jungermanniay and he suggests that the conditions under

Fig. 51.— a, Germination of Lejeuma serpyllifoUa ; B, young plant of Raduia complanata (Dum.) ;
jr, the apical cell (all the figures after Goebel).

which germination takes place probably affect to a considerable
extent the form of the protonema. This is well known to be
the case in Ferns.

The very peculiar modifications observed in certain tropical
Hepaticae, especially by Spruce and Goebel, should be
mentioned in this connection. In these forms the protonema
is permanent and the leafy gametophore only an appendage
to it. In Protocephalozia ephemeroides^ a species discovered by
Spruce in Venezuela, the plant forms a dense branching
filamentous protonema much like that of the true Mosses,
which it further resembles by having a subterranean and an
aerial portion. Upon this confervoid protonema are borne the
leafy gametophores, which are small and appear simply as buds.

MOSSES AND FERNS

CHAP.

Among the other remarkable forms is Lejeunia metzgeriopsisy a
Javanese species discovered by Goebel growing upon the leaves
of various epiphytic Ferns. It has a thallus much like that of
MetzgeriUy and like it has a two-sided apical cell. This thallus
branches extensively (Fig. 52, A), and propagates itself by

Fig. 52. — A, Ltjei4nia meizgeriopsis (Goebel), showing the thalloid protonema with terminal leafy
buds {Jj)y X 14 (after GoebclX B, Gemnia of ColoUjeunia Gocbelii.

numerous multicellular gemmae. This thallose condition is,
however, only maintained during its vegetative existence.
Previous to the formation of the sexual organs, the two-sided
apical cell of a branch becomes three-sided, as in the young
plant of other species of Lejeunia^ and from this three-sided

THE JUNGERMANNIACEyE

III

apical cell a short leafy branch, bearing the sexual organs, is
produced.^

Considerable variety is exhibited by the leaves of the
Acrogynae as to their form and position, but all agree in their
essential structure and early growth. The two lobes may be
either equal in size or unequal. In the latter case either the
dorsal or ventral lobe may be the larger, 'when the leaves are
overlapping, as occurs in most genera. Where the dorsal half
is the larger it covers the ventral lobe of the leaf in front of it,
and the leaves are said to be " incubous " ; where the reverse is
the case, the leaves are " suc-
cubous." These dififerences
are of some importance in
classification.

In many species, especi-
ally the tropical epiphytic
fornis, one lobe of the leaf
frequently forms a sac - like
organ, which appears to serve
as a reservoir for moisture.
These tubular structures some-
times have the opening pro-
vided with valves, which open
readily inward, but not from
the inside, and thus securely
entrap small insects and crus-
taceans which find their way
into them. Schififner^ com-

Fic. 53. — MastigohryMtn trilobatum (Necs).
Longitudinal section of the stem, showing the
endogenotis origin of the branches; jr, the
apical cell of the branch, X 245 (after LeitgebX

pares them to the pitchers of
a Sarracenia or Darlingtonia^
and suggests that they may serve the same purpose.

The branching of the foliose Jungermanniaceae has been
carefully investigated by Leitgeb, and will briefly be stated here.
Two distinct forms are present, terminal branching and inter-
calary. The former has already been referred to, but it shows
some variations that may be noted. In most cases the whole
of the ventral part of a segment, which ordinarily would produce
the ventral lobe of a leaf, forms the rudiment of the branch, so

* For a complete account of these forms as well as others, see Goebel's papers in
the Annals of the Bttitenzorg Botanical Gardeny vols. vii. and ix., and in Flora^
1889 and 1893. ' Schiffner (i), p. 65.

112 MOSSES AND FERNS chap.

that the leaf, in whose axil the branch stands, has only the
dorsal lobe developed. In the other case, only a part of the
cell is devoted to forming the branch, and the rest forms a
diminished but evident ventral leaf-lobe, in whose axil the
young branch is situated. The formation of the intercalary
branches, which are for the most part of endogenous origin,
may be illustrated by Mastigobryutn^ where the characteristic
flagellate branches arise in this manner. Here the apical cell
of the future branch (the branches in this case arise in strictly
acropetal order) springs from the ventral segment, and exactly
in the middle. It is distinguished by its large size, and is
covered by a single layer of cells (Fig. 53). In this cell the
first divisions establish the apical cell, which then grows in the

usual way. The young
bud early separates at
the apex from the
overlying cells, which
rapidly grow, and form
a dome-shaped sheath,
between which and the
bud there is a space of
some size. Later the
young branch grows
more rapidly than the
P ^r . _i- r t. ,^.., sheath and breaks

Fig. 54.— Ventral surface of the stem of Chiloscypkus com-

binatus (N. von E.), showing amphigastria (ow), x 14 (after thrOUgh it.

^^^'^^""^ The non-sexual

reproduction of the acrogynous Hepaticae may be brought
about either by the separation of ordinary branches through
the dying away of the older parts of the stem, or in a
few cases observed^ new plants may arise directly from
almost any point of a leaf or stem. Gemmae are known in a
large number of species. These in most of the better
known cases are very simple unicellular or bicellular buds
arising often in great numbers, especially from the margins
and apices of leaves. Curious discoid multicellular gemmse
have been discovered in a number of species, especially
in several tropical ones investigated by Goebel.^ The gemmae
upon the thallus of Lejeunta metsgeriopsis are of this character,
and similar ones are found in Cololejeunia Goebelii. In the
» Schiffner (i), p. 67. a Goebel (15).

IV THE JUNGERMANNIACEyE 1 13

latter (Fig. 52, B) the gemma is a nearly circular cell plate
attached to the surface of the leaf by a stalk composed of a
single cell. The first wall in the young gemma divides it into
two nearly equal cells, in each of which a two-sided apical cell
is formed, so that like the gemma of Marchantia there are two
growing points. There are usually four cells that differ from
the others in their thicker walls and projecting on either side
of the gemma above the level of the other cells. These serve
as organs of attachment, perhaps by the secretion of mucilage,
and by them the young plant adheres to the surface of the
fern leaf upon which it grows. The development of the
gemmae, whether unicellular or multicellular, follows very closely
that of the germinating spores.

Classification of the Jungermanniacea Acrogynce

In attempting to classify this immense family, great
difficulties are encountered. While they show a considerable
amount of variation, the differences are not constant, and the
forms merge so one into another that a satisfactory subdivision
of the group seems almost hopeless! In regard to essential
characters, such as the growth of the stem, origin and structure
of the sexual organs and sporogonium, they show remarkable
uniformity, and evidently constitute a most natural group,
allied very closely to the anacrogynous forms, as we have
already attempted to show. The latest attempt to classify
them is that of Schiffner,^ who confesses how difficult, perhaps
impossible, a satisfactory arrangement is. He proposes eight
subdivisions, as follows: I. Epigoniantheae ; II, Trigonantheae ;
III. Ptilidioideae ; IV. Scapanioideae ; V. Steph^minoideae ; VI.
Pleurozioideae ; VII. Bellincinioideae ; VIII. Jubuloideae.

» Schiffner (I), p. 22.

CHAPTER V

THE ANTHOCEROTEiE

This order contains but three genera, Anthoceros^ DeudroceroSy
and NotothylaSy and differs in so many essential particulars
from the other Hepaticae that it may be questioned whether it
should not be taken out of the Hepaticae entirely and given a
place intermediate between them and the Pteridophytes. All
the members of the order correspond closely in the Structure of
the gametophyte, and while showing a considerable variation in
the complexity of the sporophyte, there is a perfect series froai
the lowest to the highest in regard to the degree of develop-
ment of the latter, so that the limits of the genera, which
depend almost entirely upon the sporophyte, are difficult to
determine. The Anthoceroteae are of extraordinary interest
morphologically, as they connect the lower Hepaticae on the
one hand with the Mosses, and on the other with the vasculac
plants. Leitgeb^ has endeavoured to show that they are
sufficiently near to the Jungermanniaceae to warrant placing
them in a series with that order opposed to the Marchantiaceae,
but a careful study of both the gametophyte and the sporophyte
has convinced me that this view cannot be maintained ; and
that while probably the affinities of the Anthoceroteae are ^\^th
the anacrogynous Jungermanniaceae rather than with tlm*
Marchantiaceae, nevertheless the two latter orders are much
nearer each other than the former is to either of them.
^, The gametophyte in all the forms is a very simplie ttttUln^,
y^/v /either with or without a definite midrib. Of the three genera
Dendroceros is confined to the tropical regions, while the other

^ Leitgeb (7), vol. v, p. 9.

CHAP. V THE ANTHOCEROTE^ 115

genera occur in the temperate zones, but are more abundant in
the warmer regions, where they also reach a greater size. The
species of Anthoceros and Notothylas grow principally upon the
ground in shady and moist places, and are not well adapted
to resist dryness.

A marked peculiarity of their structure is the character of
the chloroplasts. There is as a rule but a single large flattened
chloroplast in each cell, such as occurs in a good many cbn-
fervoid Algae, e,g, Coleochcete^ Stigeoclonium^ and others, but, so
far as I know, is found elsewhere among the Archegoniatae
only in certain cells of Selaginella. Simple thin - walled
rhizoids are formed abundantly upon the ventral surface, where
there are in many species curious stoma-like clefts which open
into cavities filled with a mucilaginous secretion, and in some
of which, in all species yet examined, are found colonies of
^Nos^ which form dark blue -green roundish masses, often
Targe enough to be readily detected with the naked eye, and
which were formerly ^ supposed to be gemmae.

The sextfal organs are very different from those of the
other Hepaticae, and are more or less completely sunk in the
thallus from the first. While, the first divisions in the
archegonium are much like those in the other Hepaticae, the
subsequent ones are much less regular except in the axial row
of cells, and the limits of the outer neck-cells are in the
subsequent stages difficult to determine, and the archegonium
projects very little above the surface of the thallus, even when
full grown. The divisions in the axial row of cells correspond
to those in the other Archegoniatae.

The origin of the antheridium is entirely different from
that of all other Bryophytes, but shows, as will be seen later,
certain suggestive resemblances to that of the lower Pteri-
dophytes. Instead of arising from a superficial cell, as in all
of the former, the antheridium, or in most cases the group of
antheridia, is formed from the inner of two cells arising by the
division of a superficial one. The outer one takes no part in
the formation of the antheridia, but simply constitutes part of
the outer wall of the cavity in which they develop.

While the gametophyt^f is extremely simple in structure,
being no more complicated than that of Aneura or Metzgeria^
the sporophyte reaches a degree of complexity not equalled by
* Hofmeister (i), p. 18.

ii6 MOSSES AND FERNS chap.

any of the other Bryophytes. Here, instead of the greater
part of the sporogonium being devoted to spore formation, and
the sporogonium dying as soon as the spores are scattered, the
archesporium, especially in the higher forms, constitutes but a
small part of the sporogonium, which develops a highly
differentiated system of assimilating tissue, with complete
stomata of the same type as those found in vascular plants ;
and in addition a central columella is present whose origin and
structure point to it as possibly a rudimentary vascular bundle.
In all of them this growth of the sporogonium is not concluded
with the ripening of the first spores, but for a longer or
shorter time it continues to grow and produce new spores.
This reaches its maximum in some species of Anthoqeros, where
the sporogonium may reach a length of several centimetres,
and continues to grow as long as the gametophyte remains
alive. In these forms the foot is provided with root-like
processes, which are closely connected with the cells of the
gametophyte, from which nourishment is supplied to the
growing sporophyte. •

The archesporium produces spores and elaters, but the
latter are not so perfect as in most of the Hepaticas.
They often show a definite position with regard to the
spore mother cells ; this is especially marked in Notothy/as,
The archesporium in all forms that have been completely
investigated arises secondarily from the outer cells of the
capsule. Leitgeb's^ conjecture that in Notothylas the whole
central part of the capsule is to be looked upon as the
archesporium, is not confirmed by my observations on N.
valvata {orbicularis)^ where the formation of a columella and
the secondary development of the archesporium are exactly as
in Anthoceros} It is hardly likely that in the other species
there should be so essential a difference as would be implied
by such an assumption. The development of the spores and
their germination show some peculiarities which will be .con-
sidered when treating of these specially. The sporogonium
shows no clear separation into seta and capsule, all except the
foot and a very narrow zone above it producing spores. At
maturity it opens longitudinally by two equal valves, between
which the columella persists. The splitting is gradual and
progresses with the ripening of the spores.

* Leitgeb (7), vol. v. p. 49. ' See also Mottier (2).

V THE ANTHOCEROTE^ 117

The type of the order, Anthoceros^ includes fifteen to twenty
species distributed over the wcypld, but especially luxuriant in
the tropics. The species that has been most studied is the
cosmopolitan A. IcBviSy which has been the subject of repeated
investigations by numerous botanists. This species was carefully
examined by the writer, as^ well as the larger A, fusiformis,
a common Californian species allied to A, punctatus. The
^\ gametophyte is a fleshy dark -green or sometimes yellowish
^^\green thallus, which branches dichotomously, so that it often
^v^ forms orbicular discs like those of the Marchantiaceae, but owing
to the very rapid division of the growing points, and the irregular
form of the margin, the individual apices are not usually
recognisable. The thallus is either smooth, as in A. IcsviSy or it
is very much crisped and roughened by ridges and spines upon
the upper surface. Op cutting into the plant great quantities
of colourless mucilage escape. Here and there, scattered through
it, are dark blue -green specks, the Nostoc colonies always
found in the thallus. Colourless root -hairs fasten it to the
ground. No indications of the sexual organs can be seen from
the outside, and it is sometimes difficult to procure them for
study, as in both species their formation ceases very soon after
the sporogonia begin to develop, and when these are large
enough to be seen with the naked eye it is too late to procure
the young sexual organs.

The sporogonia are produced in great numbers, especially
in A, fusiforntis (Fig. 55, A), where they reach a length
of 5 to 6 centimetres, or even more, and stand so closely
together that a patch of fruiting plants has the appearance
of a tuft of fine grass. In California the plants are annual.
The spores germinate in the autumn with the commence-
ment of the winter rains, and the sexual organs are mature
by about the middle of January. As soon as fertilisation
is effected the development of sexual organs ceases, and the
regular apical growth stops, the margin of the thallus growing
out irregularly beyond the young sporogonia, which are thus
left some distance from the margin. After they are once formed
they grow as long as the thallus remains alive, and this, in
California, usually continues until about the 1st of May, when
with the cessation of rain the thallus gradually dries up. I saw
no evidences of the thallus surviving the dry season, as is the
case with Riccia and Targionia.

CHAP. V THE ANTHOCEROTEJE, 119

In order to study the apical growth satisfactorily, young
plants that show no signs of the sporogonia should be selected.
In A, fusiformis such a plant will show the margin of the
thallus occupied by numerous growing points separated by a
greater or smaller number of intervening cells. It is somewhat
difficult to determine positively whether one or more apical cells
are present. In sections parallel to the surface the initial cells
are seen to occupy the bottom of a shallow depression (Fig.
56, C). In the case figured, ;i: probably is the single apical cell,
and it seems likely that this is usually the case, although
Leitgeb ^ was inclined to think that there were several marginal
cells of equal rank. The outer wall of the cells shows a very
marked cuticle. A vertical section passing through one of the
growing points (Fig. 57) shows that the apical cell is much
larger than appears from the transverse section. On comparing
the two sections it is evident that its form is the same as in the
Marchantiaceae or Pallavidnia, Two sets of lateral segments,
and two sets of inner ones, alternately ventral and dorsal, are cut
off, and the further divisions of these show great regularity,
this being especially the case in the dorsal and ventral segments.
Each of these first divides into an inner and an outer cell. The
former divides repeatedly and in both segments forms the
central part of the thallus. It is these cells that, according to
Leitgeb,^ later show thickenings upon their walls somewhat like
those met with in many Marchantiaceae. From the outer cells
are developed the special superficial organs both on the ventral
and dorsal sides. From the former arise the colourless delicate
root-hairs and peculiar stoma-like organs, the mucilage clefts,
first described by Janczewski,* who also pointed out the true
nature of the Nostoc colonies found within the thallus. These
mucilage clefts, especially in their earlier stages, resemble closely
the stomata of the higher plants. They arise by the partial
separation of two adjacent surface cells close to the growing
point, and often at least the two cells bounding the cleft are
sister cells. However, the same division of the neighbouring
cells frequently occurs without the formation of a cleft, and there
is nothing to distinguish the two cells bounding the cleft from
the adjacent ones, and a homology with the real stomata on the
sporogonia is not to be assumed. The mucilage slit becomes

^ Leitgeb (7), vol. v. p. 13. * Leitgeb, l.c,

' Janczewski (i).

I20

MOSSES AND FERNS

wider, and beneath it an intercellular space is formed which
widens into a cavity whose cells secrete the abundant mucilage
filling it This mucilage escapes through the clefts and covers

Fig. 56. — Anthoceros ftisi/ormis (Aust.). A, Young plant with single growing point {x\ X85; B,
homontal section of the growing point of a similar plant, X525 ;.-r, the single apical cell ; C,
similar section of a growing point from an older plant, with possibly more than one initial cell*
X 360 ; D, a mucilage slit from the ventral side of the thallus, X 525.

the growing point in the same way as that secreted by the
glandular hairs in the Jungermanniacea.

Each cell of the thallus contains a single chloroplast which
may be either globular or spindle-shaped, or more or less

122 MOSSES AND FERNS chap.

flattened. The nucleus of the cell lies in close contact with the
chloroplast, and usually partly or completely surrounded by it.
There is no separation of the tissues into assimilative and
chlorophylless, as in the Marchantiaceae, and in this respect
Aniftoceros approaches the simplest Jungermanniaceae, as it does
in the complete absence of ventral scales or appendages of any
kind, except the rhizoids.

The infection of the plant with the Nostoc has been carefully
studied by Janczewski^ and Leitgeb.* The infection takes
place while the plant is young, and is usually brought about by
a free active filament of Nostoc making its way into the
intercellular space below the mucilage slit, through whose
opening it creeps. Once established, the filament quickly
multiplies until it forms a globular colony. The presence of
the parasite causes an increased growth in the cells about the
cavity in which it lies, and these cells grow out into tubular
filaments which ramify through the mass of filaments, and be-
come so interwoven and grown together that sections through
the mass present the appearance of a loose parenchyma,
with the Nostoc filaments occupying the interstices. Other
organisms, especially diatoms and Oscillarece, often make their
way into the slime cavities, but according to Leitgeb's investi-
gations their presence has no effect upon the growth of the
- thallus.

The plants are monoecious in A, fusiformis^ and this is
true of other species observed. In the former, however, the
antheridia appear a good deal earlier than the archegonia. . I
observed them first on young plants grown from the spores,
that were not more than 3 mm. in length. The exact origin
of the cell from which th« antheridia develop could not be
made out, as none of my sections showed the youngest stages.
Waldner's^ observations upon A, lavts^ however, and my
own on Notothylas valvata^ as well as a study of the older
stages in A,fusiformis, leave no doubt that in this species as
in the others the antheridia are endogenous, and the whole
group of them can be traced back to a single cell. They arise
close to the growing point, and the cell from which they arise
is the inner of two cells formed by a transverse wall in a
surface cell. The outer cell (see figure of Notothylas) divides

^ Janczewski (i). * Leitgeb (7), vol. v. p. 15.

* Waldner (2) ; see also Leitgeb (7), vol. v. p. 15.

V THE ANTHOCEROTEAi: 123

almost immediately by another wall parallel with the first, so
that the group of antheridia is separated by two layers of cells
from the surface of the thallus. The inner cell does not at
once develop into an antheridium, at least in most species,
although in the case of a doubtful species, probably A. Vincen-
tianus from New Zealand, Leitgeb^ found normally but one
antheridium in each cavity. The cell divides first by a longi-
tudinal wall into two, each of which generally divides again, so
that there are four antheridium mother cells, all, however, unmis-
takably the product of a single cell, and if a comparison is to
be made with the antheridium of any other Liverwort, the
antheridium in the latter is homologous, not with the single
one of Ant/toceroSy but with the whole group, plus the two-
layered upper wall of the cavity in which they lie.

The first divisions in the antheridium are the same as those
in the original cell, ue, the young antheridium is divided longi-
tudinally by two intersecting walls, and the separation of the stalk
from the upper part is secondary ; indeed in the earliest stages
it is difficult to tell whether these longitudinal divisions will result
in four separate antheridia or are the first division walls in a
single one. Secondary antheridia arise later by budding from
the base of the older ones, so that in the more advanced con-
ditions the antheridial group consists of a varying number, in
very different stages of development (Fig. 58). After the first
transverse walls by which the stalk is separated, the next
division in each of the upper cells is parallel to it, so that the
body of the antheridium is composed of nearly equal octant
cells. Then by a periclinal wall each of these eight cells is
divided into an inner and an outer cell, and the eight central
ones then give rise to the spernuicells, and the outer ones to
the wall. The four stalk cells by repeated transverse divisions
form the four-rowed stalk found in the ripe antheridium. The
uppermost tier of the stalk has its cells also divided by vertical
walls and forms the basal part of the antheridium wall. The
transverse and vertical division walls in the central cells alter-
nate with great regularity, so that there is little displacement
of the cells, and up to the time of the separation of the sperm
cells the four primary divisions are still plainly discernible, and
the individual sperm cells are cubical in form. In the peri-
pheral cells hardly less regularity is observable. Except near
* Leitgeb (7), vol. v. p. 17.

124

MOSSES AND FERNS

CHAP.

the apex none but radial walls are formed after the first trans-
verse wall has divided the body of the antheridium into tw-o
tiers, and when complete the wall consists of three well-marked
transverse rows of cells, the lower being derived from the upper-
most tier of stalk cells. At the apex the cells are not quite so
regular (Figs. D, E). In its younger stages the antheridium
is very transparent and perfectly colourless. In each peripheral
cell a chloroplast is evident, but at this stage it is quite colour-
less and the nucleus is very easily seen in close contact with it.

Fig. 58. — Anthoceros fusi/ormis (Aust.). Development of the antheridium ; D, E, drawn from
livins specimens, the others microtome sections ; D, i, shows the single chloroplast in each of the
wall cells, and the secondary antheridium {s) budding out from its base ; a is an optical section
of the same ; E, surface \'iew of full-grown antheridium ; F, cross-section of a younger one. Figs.
A, E Xaas, the others X450. ^

As the antheridium grows the chloroplasts develop with it,
becoming much larger and elongated in shape, and at the same
time develop chlorophyll. The mature chloroplast is a flattened
plate that nearly covers one side of the cell, and its colour has
changed from green to a bright orange as in the antheridium
of many Mosses. The sperm cells are discharged through an
opening formed by the separation of the apical cells of the
antheridium. These cells do not become detached, and return
to their original position, so that the empty antheridium has its

V THE ANTHOCEROTE^ 125

wall apparently intact. The spermatozoids are small and
entirely like those of the other Hepaticae.

Leitgeb ^ found in abnormal cases that the antheridia might
arise superficially, as in the other Hepaticae. Whether this is
a reversion to the primitive condition would be hard to say,
but it is at any rate possible.

At first the cell from which the antheridial complex arises
is not separated from its neighbours by any space. About
the time that the first divisions in it are formed, the young
antheridial cells begin to round off and separate from the
cells above them. With the growth of the surrounding cells
this is increased, so that before the divisions in the separate
cells begin, the group of papillate cells is surrounded by a
cavity of considerable size. To judge by the readiness with
which the walls of the cavity stain, it is probable that the
separation of the cells is accompanied by a mucilaginous
change in their outer layers.

i/^The first account of the archegonium was given by Hof-
meister, who, however, overlooked the peripheral cells and only
saw the axial row. Later Janczewski ^ showed that Anthoceros
did not differ essentially in the development of the archegonium
from the other Hepaticae, and his observations were confirmed
by the later researches of Leitgeb ^ and Waldner.^ The forma-
tion of archegonia does not begin until the older antheridia are
mature, and very often, especially in A, IceviSy few or no
antheridia were found on the plants with well -developed
archegonia. After the formation begins, each dorsal segment
gives rise to an archegonium, so that they are arranged in quite
regular rows, in acropetal order. After the transverse wall by
which the segment is divided into an inner and an outer cell is
formed, the outer cell becomes at once the mother cell of the
archegonium, much as in Aneura, In this cell next arise three
vertical intersecting walls, by which a triangular (in cross-
section) cell is cut out as in the other Hepaticae. Sometimes
it looks as if one of these walls was suppressed, but even in
such cases the triangular form of the central cell is evident.
The main difference between the archegonium at this stage in
Anthoceros and the other Hepaticae lies in the complete sub-
mersion of the archegonium rudiment in the former. In this

* Leitgeb (7), vol. v. p. 19. / ' Janczewski (2).

' Leitgeb (7), vol, v. p. 19. * Waldner (2).

126

MOSSES AND FERNS

CHAP.

respect Aneura, where the base of the archegonium is confluent
with the cells of the thallus, offers an interesting transition
between the other Hepaticae, where the base of the archegonium
is entirely free, and Anthoceros,

The archegonium rudiment divides into two tiers as in the
other Liverworts, and the peripheral cells divide longitudinally,
and here too the neck shows the six vertical peripheral rows
although it is completely sunk. Later, the limits of the neck
become often hard to determine, although by later divisions the
central cell is surrounded by a pretty definite layer of cells. The
axial cell divides into two of nearly equal size, but the inner one
soon increases in breadth more than the upper one. The latter
divides again by a transverse wall into an outer cell correspond-
ing to the cover cell of the ordinary hepatic archegonium, the
other to the primary neck canal cell. The cells of this central
row soon become clearly different from the other through their
more granular contents. The lower cell grows much faster
than the others and divides into the egg cell and the ventral
canal cell. The cover cell divides by a vertical wall into two
nearly equal cells, and these usually, but not always, divide
again, so that four cells arranged cross-wise form the apex of the
archegonium. In A, fusiformis in nearly ripe archegonia I
have sometimes been able to see but two of these cover cells,
but ordinarily four are present. The neck canal cell divides
first into two, and these then divide again, so that four cells are
formed. This was the ordinary number in A, fusiformis. In
a nearly ripe archegonium of A. IcBvis five neck canal cells were
seen, but in no cases so many as Janczewski ^ describes for this
species, where he says as many as twelve may be present.

If the earlier divisions in the archegonium of Anthoceros are
compared with those of the other Hepaticae, the most striking
difference noticed is the separation of the cover cell. In the
latter the first division of the axial cell separates the cover cell
from an inner one, and by the division of the latter the primary
neck canal cell is cut off from the central cell. In Anthoceros
the neck canal cell is cut off from the outer, and not from the
inner cell.

As the archegonium approaches maturity the cover cells
become very much distended and project strongly above the
surrounding cells. In stained microtome sections their walls
^ Janczewski (2), p. 415.

THE ANTHOCEROTE^

127

colour very strongly, showing that they have become partially
mucilaginous. This • causes them to separate readily, and they
are finally thrown off, so that in the open archegonium no trace
of them is to be seen. The walls of the canal cells and the
central cell undergo the same mucilaginous change, but here it
is complete, and before the archegonium opens the partition
walls of the canal cells completely disappear, and the neck con-
tains a row of isolated granular masses corresponding in number
to the canal cells. The ventral canal cell is quite as large as
the egg, which consequently does not nearly fill the cavity at

Fig. isg,—Anihoceros/usi/ormu (Aust.). A, two-celled embryo within the archegonium venter,
x6oo ; B, C, two longitudinal sections of a four-celled cmbr>'0, X600.

the base of the open archegonium (Fig. 57, D) after the canal
cells have been expelled. The egg did not, in any sections
studied, show clearly a definite receptive spot, but appeared to
consist of uniformly granular cytoplasm with a nucleus of
moderate size. The upper neck cells in the open archegonium
become a good deal distended, and the canal leading to the
egg is unusually wide. Surrounding the central cavity the
cells are arranged in a pretty definite layer.

Hofmeister was the first to study the development of the
embryo in Anthoceros^ and described and figured correctly the

128 MOSSES AND FERNS chap.

first divisions, but his account of the apical growth, which he
supposed was due to a single apical cell, and the differentiation
of the archesporium, was shown by the careful investigation of
Leitgeb^ to be erroneous. The following account is based
upon a large series of preparations of A. Icevis and A,fusiformiSy
which seem to agree in all respects. After fecundation the
egg at once develops a cellulose wall and begins to grow until
it completely fills the centre cavity of the archegonium. As it
grows the uniformly granular appearance of the cytoplasm dis-
appears, and large vacuoles are formed, so that the whole cell
appears much more transparent. The granular cytoplasm is
now mainly aggregated about the nucleus, which has also
increased in size (Fig. 57, E). The first division wall is parallel
with the axis of the archegonium and divides the embryo into
two equal parts, in which the character of the cells remains much
as in the undivided ^%^. Here too the granules are most
abundant about the nucleus, from which radiate plates that
separate the vacuoles. The next divisions are transverse and
divide the embryo into two upper large cells and two lower
smaller ones. The embryo at this stage is oval and more or
less pointed above. In each of the four primary cells vertical
walls arise that divide the embryo into octants, but the upper
octants are decidedly larger than the lower. Next, in the upper
cells, transverse walls are formed and the embryo then consists
of three tiers of four cells each. Of these the cells of the upper
tier are decidedly the larger. At this stage, in neither species
examined by me, were any traces present of the projection of
the basal cells figured by Leitgeb.^ As his drawings were
made from embryos that had been freed from the thallus,
probably with the aid of caustic potash, it is quite possible that
this appearance was due in part at least to the swelling of the
cell walls through the action of the potash. At any rate in
microtome sections of both species in these early stages, the
basal cells do not project in the least (Fig. 60, A). The next
divisions are very uniform in the upper tier of cells, from which
the capsule develops, but less so for the two lower ones. In
the upper tier, seen in cross-section (Fig. 60, B i), a slightly
curved wall running from the median wall to the periphery
forms in each quadrant, which thus viewed is divided into an
inner four-sided and an outer three-sided cell. In the former a
^ Leitgeb (7), vol. v. * Leitgeb (7), vol v. PI. I.

THE ANTHOCEROTE^

129

periclinal wall next forms, which cuts off an inner square cell
(Fig. 60, D). In longitudinal section these periclinal walls are
seen to be concentric with the outer walls of the cells, and to
strike the median and quadrant walls at some distance below
the apex of the sporogonium so as to completely enclose the
central cells (Fig. 60, C). By the formation of these first
periclinal walls the separation of the columella from the wall of

Fig. 6a — Anthoccros laitis (L.). Development of the embryo, X300 ; A, C, E, median longitudinal
sections ; B and D, successive cross-sections of embryos of about the age of A and C respectively.
In £ the archesponum is differentiated.

the capsule is completed, and this is not unlike what obtains in
the sporogonium of many other Hepaticae ; but an essential
difference must be observed. In the latter the central group
of cells forms the archesporium ; here these cells, as we shall
see, take no part in spore formation. In the lower tiers of
cells similar but less regular divisions occur (Fig. 60, D 2), and
the outer cells begin to grow out into root-like processes which
push down among the cells of the thallus and obviously serve

I30 MOSSES AND FERNS chap.

the purposes of haustoria. Leitgeb ^ states that the foot arises
only from the lowest of the primary tiers of cells, but in most
of my sections of the earlier stages the fact that the foot was
composed of two distinct layers of cells, corresponding in
position to the two lower tiers of cells in the embryo, was very
obvious (Fig. 60, E).

The origin of the archesporium in Anthoceros was in
the main correctly shown by Leitgeb,^ but I find that the
extent of the archesporium is less than he represents. In
PI. I. Figs. 3 and 10 of his monograph on the Anthoceroteae,
he figures the archesporium as extending completely to the
base of the columella. A large number of sections were
examined, and in no case was this found to be so. Instead, it
was only from the cells surrounding the upper half of the
columella that the archesporium was formed. Previous to the
differentiation of the archesporium the four primary cells of the
columella divide by a series of transverse walls until there are
about four cells in each row. Radial walls also form in the
outer cells so that their number also increases, and the young
capsule consists of the central columella composed of four rows
of cells and a single layer of cells outside. The archesporium
now arises by a series of periclinal walls in the peripheral cells of
the upper half only of the capsule, and is thus seen to arise from
the peripheral cells of the capsule, and not from the central ones.
Fig. 60, E shows a longitudinal section of the spor^onium at
this stage. Three parts may be distinguished — tfie foot, the
capsule, and an yitermediate zone between. ^.Tliis latter is
important, as it is from this that the meristematic part of the
older sporogonium is formed. With the separation of the
archesporium the apical growth ceases, and the future growth
is intercalary. •

In the capsule cell, divisions proceed rapidly in all its parts.
The original four rows of cells forming the columella increase
to sixteen, which is the normal number in the fully-developed
sporogonium. The archesporium, by the formation of a second
series of periclinal walls, becomes two-layered, and the wall
outside the archesporium becomes about four cells thick, the
outermost layer forming a distinct and well-developed epidermis.

The foot grows rapidly in size, but the divisions are
very irregular, and finally it forms a large bulbous ap-

* Leitgeb (7), vol. v. ^ Leitgeb, /.r.

THE ANTHOCEROTE^

131

pendage to the base of the sporogonium. The cells are
large and the outer ones develop still further the root-like char-
acter of those in the young foot. The tissues of the thallus
about the base of the sporogonium grow rapidly with it, and
the connection between the surface cells of the sporogonium
foot and the adjacent cells of the thallus is very intimate.

The subsequent growth of the cap-
sule is entirely dependent upon the
activity of the zone of meristem at
its base. This divides very actively,
and the divisions correspond exactly
with the primary ones in the young
embryo, so that the completed portions
of the older parts of the capsule are
continuous with the forming tissues at
the base. A series of cross-sections at
different points, compared with a median
longitudinal section, shows in a most
instructive way the gradual development
of the different parts of the mature
capsule (Fig. 62). The centre of the
sporogonium is occupied by a colu-
mella composed of sixteen rows of cells,
which in cross-section form a nearly
perfect square. At the base these cells
are thin -walled and show no intercell-
ular spaces, but farther up their walls
begin to thicken and the rows gradually
separate until in the upper part the fig. (>x.-Anthoceros utvis (l.).
columella has somewhat the appearance Median longitudinal section

r • 1 ^ J r:i_ T-t. through the base of the sporo-

Of a bundle of isolated nbreS. Ine gonium. The archesponum is

archesporium is constantly growing from
below, and the new cells are cut off
from those surrounding the columella in the same way as at
first. The archesporium, as well as the columella, can be
traced down nearly to the base of the capsule, and its cells are
very early recognisable both by their position and by their
contents. At first but one cell thick, the archesporium soon
becomes double, but does not advance beyond this condition.
As the archesporium is followed from the base towards the
apex of the capsule the cells begin to show a differentiation.

shaded. F, Foot; r,
sheath, xxoo.

basal

CHAP. V THE ANTHOCEROTEjE 133

Up to the point where the archesporium becomes divided
into two layers the cells appear alike ; but shortly after this
their walls begin to separate, and two distinct forms are re-
cognisable, arranged with much regularity in many cases,
although this arrangement is not invariable. Pretty regularly
alternating are groups of oval, swollen cells, with large nuclei
and abundant granular cytoplasm, and much more slender ones,
that may undergo secondary longitudinal divisions. The
latter have smaller nuclei and more transparent contents.
Examination higher up shows that the former are the spore
mother cells, the others the elaters, which here have the char-
acter of groups of cells, and do not develop the spiral thicken-
ings found in most Hepaticae. As these two sorts of cells
grow older they separate completely, and the spore mother
cells become perfectly globular. The sterile cells remain more
or less united, and form a sort of network in whose interstices
the spores lie.

The development of the spores can be easily followed, at
least in most of the details, in fresh material, and on this
account it was among the first plants in which cell division was
studied.^ The mother cells in all stages can be found in the
same sporogonium, and on account of their great transparency
show the process of cell division very satisfactorily. The
nucleus, however, is small, and its behaviour during the cell
division is not so easy to follow. Strasburger ^ has described
this at length, and I can confirm his account. The mother cell,
just before division, is filled with colourless cell sap, and the
cytoplasm is confined to a thin film lining the cell wall. This
cytoplasmic layer is somewhat thicker on one side, and here
the nucleus is situated (Fig. 63, A). Lying close to the nucleus
is a roundish body, of granular consistence and yellowish green
in colour. This is a chloroplast, which at this stage is less
deeply coloured than later. The chloroplast contains a number
of granules, some of which are starch. The cell increases
rapidly in size, and the nucleus, together with the chloroplast,
moves away from the wall of the cell toward the centre, where
they are suspended by cytoplasmic threads. The chloroplast
next divides into two equal portions, which move apart (Fig.
63, B), but remain connected by the cytoplasmic filaments.
They approach again, and each dividing once more, the four

* Strasburger (9), p. 158. • ' Strasburger, Lc, p. 161.

134

MOSSES AND FERNS

resulting chloroplasts remain close together with the nucleus,
in the centre of the cell.

Owing to the small amount of chromatin in the nucleus,
the karyokinetic figures are small and the changes difficult to
follow satisfactorily. Enough can be easily made out, however,
to show that the process is in no way peculiar. There is first
a nuclear spindle of the ordinary form, and the resulting nuclei
assume the resting stage before dividing again. Each then
divides again, and the four nuclei move to points equidistant
from each other, and which are already occupied by the four

chloroplasts. After this
is accomplished, cell walls
arise simultaneously be-
tween the four nuclei,
dividing the mother cell
into four tetrahedral
cells, — the young spores.
The wall of the mother
cell becomes thicker, and
in the later stages swells
up on being placed in
water, so that it interferes
a good deal with the
study of the spores in
the fresh condition. As
the spores ripen they
develop a thick exospore,
which is yellow in colour
and irregularly thickened
in A, Icevis^ and in A.
fusiformis black and covered with small tubercles. The chloro-
phyll disappears and the spore becomes filled with oil and other
food materials. The spores remain together until nearly ripe.
The elaters, if this name can properly be applied to the sterile
cells, at maturity consist of simple or branching rows of cells,
which in some cases arise from the division of a single one ; but
more commonly, at least in A, Icevis^ where they branch, it is
probable that they are to be looked upon as merely fragments
of the more or less continuous network of sterile cells. The
contents mainly disappear from the older elaters, and their
walls become thick and in colour like the wall of the spores.

Fig. 63. — Spore division in A./usi/ormis, optical sections
of living cells, X 60a

THE ANTHOCEROTEyE

135

In A, fusiformis they .are longer and more symmetrical than in
A, Icevis, and in one group of the genus, according to Gottsche,^
the elaters, which consist of a row of five to six cells, have a
distinct spiral band as in Dendroceros, Leitgeb ^ thinks, how-
ever, that this group is more nearly related to the latter genus
than to Anthoceros proper, inasmuch as in addition to the
peculiar elaters the epidermis of the capsule has no stomata,
which are always present in typical species of Anthoceros,

If the epidermis from the young capsule is examined it is
seen to be composed of elongated narrow cells much like those
in the epidermis of elongated leaves of Monocotyledons. In
the older parts some of these cells cease to elongate, and become

Fig. 64. — Ripe spores and elaters oi A, Unnsy x6oo.

more nearly oval (Fig. 65, A). These are the young stomata,
and exactly as in the vascular plants, each divides longitudinally
by a septum which later separates in the middle and forms the
pore surrounded by its two guard cells. The walls of the other
epidermal cells become much thickened and distinctly striated.
Each epidermal cell contains a single large chloroplast like that
in the cells of the gametophyte, and between the cells are well-
developed air-chambers communicating with the stomata, so that
there is here a typical assimilative system of tissues.

About the base of the growing sporogonium is a thick
tubular sheath representing in part the calyptra of the other
Hepaticae, but involving, besides the archegonium venter, also

1 Gottsche (2).

Leitgeb (7), vol. v. p. 27.

136

MOSSES AND FERNS

the surrounding tissue of the gametophyte. This sheath keeps
pace with the growth of the sporophyte for a long time, but
finally the sporogonium grows more rapidly and projects far
beyond it, and this remains as a tube surrounding its base.
The growth of the sporogonium continues as long as the
gametophyte remains alive, and in A. fusiformis is often 6
centimetres or more in length, and reaches nearly this length
before the first spores are ripe and the capsule opens. This it
does by splitting at the top into two equal valves between
which the dried -up columella protrudes. The split deepens as
the younger spores ripen, and may finally extend nearly to the
base. It is quite possible, although this point was not

investigated, that the line of
dehiscence corresponds to the
primary vertical wall in the em-
bryo, as is the case in the
Jungermanniaceae.

The germination of the
spores ^ has hitherto been ob-
served only in A, lavis. A study
of the germination in A. fusi-
formis shows a general corre-
spondence with the results of
other observers, but certain points
were brought out that do not

Fra, 6s. -^A, young; a fully developed stoma seem tO haVC bcCn obscrVCd if!

'J^^^l^^;^^^^''"^'^^^-^^^-^-'^' A. Im^is, The spores of A.fusi-

formis are protected by a perfectly
opaque black cxospore, which is covered with small spines or
tubercles. These spores will not germinate readily when fresh,
but after resting for a few months grow freely. As in other
similar spores, the exospore is ruptured along the three ridges
upon the ventral side (?>. that with which it was in contact with
the other spores of the tetrad), and through this cleft the endo-
spore protrudes as a papilla which sometimes grows into a very
long germ tube, or more commonly divides before it reaches a
great length* Into this tube passes the single chromatophore
which, during the early period of germination, has resumed its
green colour, and with it the oil drops and other contents of
the spore. A good deal of variation was observed here in the

' Hqfmcister (i) ; Gronland (i) ; Leitgeb (7), vol. v. p. 29.

THE ANTHOCEROTE^

137

first divisions, as is the case in A, Icevis, The first division
wall IS, in most cases at least, transverse, and is usually followed
by a second similar one, before any longitudinal walls appear.
Then in the end cell two intersecting walls and the formation
of four terminal quadrant cells are often seen (Fig. 66, D), as
in other Hepaticae. Variations from this type are often met
with, and some of these are shown in the figures. Very
commonly a second cell is cut off by an oblique wall from the
germ tube subsequent to the first transverse wall, but this does
not, at least in the early stages, develop into a root-hair, the

Fig. 66. — Anihoceros fusiformis (Aust.). Germination of the spores, X250. A shows a form with
very long germ tube ; in B there seems to be a definite apical cell. Fig. D, 2, is an apical view
ofD, I.

first root-hair being met with only after the young plant has
become a cell body of considerable size (Fig. 67).

Whether the young plant regularly grows from a single apical
cell is difficult to say, but it seems probable, and numerous forms
like Fig. 66, B were encountered where there certainly seemed
to be a two-sided apical cell, such as occurs so often in other
Hepaticae. At a later stage (Fig. 67, B) a single apical cell of
the form found in the mature thallus is unmistakably present.
By this time the marginal lobes that give this species its
peculiar crimped appearance begin to develop. They arise
close to the growing point, and grow rapidly beyond it, but do

138

MOSSES AND FERNS

CHAP.

not show any definite apical growth. The plant at this stage
has a striking resemblance to the prothallium of Equisetufn.
With the appearance of the marginal lobes, the first of the
mucilage slits appears upon the ventral surface (Fig. 67), and
from time to time surface cells grow out into the delicate
rhizoids, and a little later the first dichotomy of the growing
point takes place. Up to this time the young plants appeared
entirely free from NostoCy but soon after they were found to
be infected, which no doubt was connected with the formation
of the mucilage slits through which the Nostoc enters the
thallus.

Dendroceros includes about a dozen species of tropical Liver-

Fig. ^T.—Authoceros fusi/ormis (Aust.). A, Young plant showing the first rhizoid (r) ; B, upper part
of an older one with the first mucilage cleft (x/) ; x^ the growing point, X215.

worts, which are distinguished at once from Anthoceros by the
very characteristic form of the thallus. This has a massive
midrib, projecting below, but the rest of the thallus is but one
cell thick and forms lateral wings which are much folded
and lobed, so that the aspect of the plant is somewhat like a
Fossonibronia, As in Anthoceros^ some species have a perfectly
compact thallus without intercellular spaces {D, cichoraceus\
while in others these are very much developed and the thallus
has a more or less spongy texture, ix, D, Javanicus, This
development of the thallus and sporogonium has been studied
only by Leitgeb,^ and in the main seems to correspond very

^ Leitgeb (7), vol. v. p. 39.

V THE ANTHOCEROTE^ 139

closely to AntJtoceros. A difference may be noted, however, in
some details. Thus the form of the apical cell is like that of
Pellia epiphylla^ where the inner segments extend the whole
depth of the thallus, and the division into dorsal and ventral
segments is secondary. The formation of the wings begins
near the apex and is the result of the growth of the marginal
cells, which project strongly and divide rapidly by vertical
walls only. The walls of the cells are thickened at the
angles, and the surface view is curiously like a cross-section of
the collenchyma of many vascular plants. As in Anthoceros
mucilage slits are formed, sometimes on both surfaces of the
thallus, and through these the plant is infected with Nostoc^ as
in the other Anthoceroteae. In Dendroceros the Nostoc colonies
are very large and cause conspicuous swellings upon the thallus.
All the species of Dendroceros, according to Leitgeb, are
monoecious, and the development of the sexual organs appears
to be the same as in Anthoceros, The antheridia are very large
and borne singly in cavities whose upper wall projects above
the surface of the midrib. So far as is known the origin and
development correspond closely to those of Anthoceros, except
that the stalk is much longer and has but two rows of cells,
which probably indicates that but one longitudinal wall is
formed in the antheridial cell before the transverse walls that
separate stalk and capsule. Gemmae occur in some species
{D, cichoraceuSy D, Javanicus\ and are roundish cell masses
developed from single cells of the lamina. So far as could be
determined from incomplete material, the conclusion was
reached by Leitgeb that Dendroceros approaches Anthoceros very
closely in the development of the sporogonium. The origin of
the columella, which usually in the later stages is composed of
more than sixteen rows of cells, and the differentiation of the
archesporium, seem to be exactly the same, and the further
development of the large bulb-like foot and the formation of
the spores and elaters are the same. The spores are larger, and
the elaters (Fig. 74, B) provided with distinct spiral bands. In
none of the species examined by Leitgeb did he find any traces
of stomata upon the capsule, and concludes that they are
entirely wanting in this genus, which in this respect, as well as
in the character of the elaters, approaches closely one section
of the genus Anthoceros, The spores, as in Pellia and
Conocephalus, germinate within the capsule, and at the time of

I40

MOSSES AND FERNS

dispersal are already multicellular. Apparently no germ tube
is formed, but the spores develop at once into a cell mass upon
which, while still very young, the mucilage clefts are developed,
and at an early stage the infection by the Nostoc cells is
effected. The growth of the older capsule and gradual develop-
ment of the spores are the same as in Anthoceros,

The third genus, Notothylas, is of especial interest, because
it was largely upon the results of his investigations upon this
plant that Leitgeb ^ based his theory of the close relationship of
the Anthoceroteae and Jungermanniaceae. All of Leitgeb's
observations on the young capsule were made from herbarium
material, and, as he himself admits, were in all cases embryos
that had not fully developed. The writer has made a very
complete examination of the commonest American species,
N. orbicularis {yalvatd)^ and the results of the study of the
development of the sporogonium differ so much from those of
Leitgeb that they will be given somewhat in detail.

The thallus much resembles a small Anthoceros, and sections
through it show that in its growth and the development and
structure of the sexual organs there is close correspondence.
The thallus contains very large lacunae, which are formed in
pretty regular acropetal order, and vertical sections show these
large cavities increasing regularly in size as they recede from
the apex. Similar but less regular lacunae occur in A, fusiformis.
The antheridia arise as in Anthoceros, endogenously. The
youngest stage found is shown in Fig. 68, A. Here evidently
the young antheridia ( cJ ) have been formed by the longitudinal
division of a single hypodermal cell, whose sister epidermal
cell has divided again by a transverse wall to form the outer
wall of the antheridial cavity (Figs. A, B). The commonest
number of antheridia formcii is four.

Less regularity is found in the next divisions than in
Anthoceros, although in the main they are the same. This is
observable both in longitudinal and cross-sections (see Fig. 68,
D). The full-grown antheridium is more flattened than in
either species of Anthoceros examined by me, and the stalk
shorter and thicker, but otherwise closely resembles it, although
the extremely symmetrical arrangement of the cells, especially
of the wall, is much less noticeable.

The archegonia correspond very closely, both in position

* Leitgeb (7), vol. v. p. 39.

THE ANTHOCEROTE^

141

and structure, with those of the other genera, the most marked
peculiarity being the more nearly equal diameter of the cover
cell and central cell, and a corresponding increase in the breadth
of the neck canal cell. Subsequently the central cell becomes
much enlarged and the appearance of the fully-developed arche-
gonium is very much like that of Anthoceros (Fig. 69, A). As
in A, fusiformis^ the usual number of neck canal cells seems to
be four, and in no case did the number exceed five. The cover
cells were four in number in all the archegonia studied, and are

Fig. fA>—Nototkyltu orbicularis (Sull.)< Development of the antheridium. D, cross-section, the
others longitudinal sections ; £, nearly ripe antheridium, X 300, the other figures X 600 ; <$ , A,
the primary antheridial cells.

larger than in Anthoceros, As in that genus, they are thrown
off when the archegonium opens.

The youngest embryo found was composed of four cells,
and presented quite a different appearance from the corre-
sponding stage in Anthoceros, It is impossible from this stage
to tell whether the first wall in the embryo is vertical or trans-
verse. This embryo consisted of four nearly equal quadrants,
instead of having the two upper cells larger than the lower
ones. By comparison with the older stages there is little
doubt that here the first transverse wall separates the foot
from the capsule, as in Sphcerocarpus^ and that the upper cell

142

MOSSES AND FERNS

CHAP.

develops directly into the capsule instead of the latter being
determined by the second transverse walls. In the next
youngest stages found (Fig. 71, B) the archesporium was
already differentiated. A comparison of this with the corre-
sponding stage of Anthoceros shows conclusively that the two
are practically identical in structure. The columella, evidently
formed as in AnthoceroSy and as there made up of four rows of
cells, is surrounded by the archesporium cut off from the peri-

FiG. 6g.—Notothyias orbicularis (Sull.). Development of the archegonium, x6oo ; a-, the apical celL

pheral cells. Leitgeb's surmise that the columella is a second-
ary formation is, therefore, for N, orbicularis at least, entirely
erroneous, and it is extremely likely that when normal speci-
mens of the other species are examined from microtome
sections, in the young stages at least, a similar columella will
be foiind. The single embryo that Leitgeb^ figures of A''.
orbicularis {valvata) is at once seen to be abnormal, and as his
conclusions were drawn from a study of similar dead embryos
1 Leitgeb (7), vol v. PI. IV. Fig. 77.

THE ANTHOCEROTE.^

in the other species, they cannot be accepted without more
satisfactory evidence. While in the main corresponding to the
embryo of Anthoceros there are some interesting differences
which are closely associated with the structure of the older
sporogonium. The foot is smaller than in Anthoceros and
derived only from the lowest tier of cells. The columella is
decidedly smaller, and the archesporium, as well as the young
sporogonium wall, relatively much thicker. As in Anthoceros, the
archesporium does not extend to the foot, but is separated by
the zone of cells which there give rise to the meristem at the

Fig. 70. — Notothylas orbicularis (SulI.X A, B, Horizontal sections of the growing point with young
archegonifi ; C, cross-section of the apex of an archegonium, showing the arrangement of the
cover cells ; D, longitudinal section of a nearly ripe archegonium, X 400.

base of the capsule. The form of the embryo is different too.
It is pear-shaped and more elongated than in Anthoceros.

As the embryo develops these differences become more
apparent and others arise. Fig. 71, C shows a stage where
the division of the archesporial cells has begun, and it is at
once apparent how much more conspicuous they are. It is
seen too that the outer cells of the upper part of the capsule
are also dividing actively, and that, compared with Anthoceros,
the apical part of the capsule retains its meristematic character
for a much longer period. Corresponding with this, the growth
at the base of the capsule is much less marked. The divisions
in the archesporium are much more active than in Antlioceros,
and also less regular. At first divisions occur in the upper
portion in all directions, so that above the columella there is

144

MOSSES AND FERNS

CHAP.

a mass of archesporial tissue much thicker than that below,
and occupying very much more space than the corresponding
tissue in Anthoceros. Longitudinal sections through the basal
part of the older sporogonium show an arrangement of tissues
similar to those in Anthoceros^ but there are differences corre-
sponding to those in the young stages. The foot (Fig. 72, A)
is much smaller and flatter, and sometimes shows a very regular
structure. The central part is composed of a compact mass of
rather large cells, between which and the base of the capsule is a
narrow zone of meristematic tissue. The superficial cells do not
always grow out into the root-like processes found in AntJtoceros

Fig. 71. — Nototkylas orbicularis i^vW.), A, Four-celled embryo ; B, C, older embryos, in longitudinal
section. The archesporial cells are shaded. A, X 450 ; B, C, X 375.

and Dendroceros, but may remain short and project but slightly.
The cells are characterised by abundant granular cytoplasm and
conspicuous nuclei, showing that they are probably not only
absorbent cells, but also elaborate the food materials taken in
from the gametophyte. The gradual transition of the differen-
tiated tissues above into the meristem at the base, is precisely
as in Anthoceros, and sections at that point in the two genera
can scarcely be distinguished from one another. The columella
(in longitudinal section) in both shows four parallel rows of
cells, outside of which lies the single row of archesporial cells,
and four rows of cells belonging to the wall of the capsule.
As the section is examined higher up, however, there are

THE ANTHOCEROTE^

145

marked differences, especially in the divisions of the arche-

sporium. The first divisions in the archesporium of Notothylas

146

MOSSES AND FERNS

CHAP.

are periclinal, and for a short distance it is two-layered, as it is
permanently in Anthoceros ; but still further up it widens very
rapidly by the formation of repeated periclinal walls, and soon
comes to be much thicker than either the columella or the capsule
wall. A further study of the developing archesporium shows
that the divisions occur with a good deal of regularity. The
archesporial cells are divided by alternating vertical and trans-
verse walls into four layers of cells instead of two, as in Anthoceros^
and these cells are arranged in regularly placed
transverse rows. At first the cells appear alike,
but later there is a separation into sporogenous
and sterile cells as in Anthoceros. Each primary
transverse row of cells becomes divided into
two. The upper row grows much faster, and
its cells become swollen and the cytoplasm
more granular, while the lower row has its cells
remaining flattened and more transparent, ix,
there is a separation of the archesporium into
alternate layers of sporogenous and sterile cells
as in AntfioceroSy but here the number of cells
is double that in the latter, and the longer axis
of the cells is transverse instead of vertical. In
the portion of the archesporium above the colu-
mella these alternate layers of spore mother
cells and sterile cells extend completely across
the cavity, and Leitgeb ^ has correctly figured
this, although he probably was mistaken in
assuming that this arrangement extended to the
base of the capsule.

The further development of the capsule is
Fig. 73.-Longitudinai ^luch like that of Ant/toccroSy but the division

section of a nearly Qf ^]^q chloroplast takes place before the spore
N.orhicuiaris, X50. mother cells are isolated, and the primary chloro-
plast is evident almost as soon as the sporogen-
ous cells are recognisable as such. The cells of the columella do
not become as elongated as in Anthoceros ^ and develop thicken-
ings much like those of the sterile cells of the archesporium,
and it was this partly that led Leitgeb ^ to the conclusion
that even where a definite columella was present it probably
arose as a secondary formation in the archesporium, similar
* Leitgeb (7), vol. v. PI. IV. Fig. yi, ^ Leitgeb (7), vol. v. p. 5a

V THE ANTHOCEROTEjE 147

to the formation of the axial bundle of elaters in Pellia,
and that in Notothylas as in the Jungermanniaceae, the arche-
sporium arose from the inner of the cells formed by the first
periclinal walls, and not from the outer ones. That this is not
true for N, orbicularis is shown beyond question from sections
of both the older and younger sporogonium, and it would be
extremely strange if the other species should differ so radically
from this one as would be the case were Leitgeb's surmise
correct.

The wall of the capsule does not develop the assimilative
apparatus of the Anthoceros capsule, and stomata are completely
absent from the epidermis. The inner layers of cells are more
or less completely disorganised, and they probably serve to
nourish the growing spores, which here, of course, are corre-
spondingly more numerous than in Antfioceros. As there, the
sterile cells form a series of irregular chambers in which the
spores lie. At maturity these sterile cells separate into irregu-
lar groups (Fig. 74, C). Their walls are marked with short
curved thickened bands, yellowish in colour like the wall of the
ripe spores. At maturity the capsule projects but little beyond
its sheath, and opens by two valves. In some species, e.g, N,
fnelanosporay the capsule often opens irregularly.

The Anthoceroteae form a most interesting series of forms
among themselves, but are also of the greatest importance in
the study of the origin of the higher plants. Unquestionably
Notothylas represents the form which comes nearest to the
other Liverworts, but until the other species are investigated
further we shall have to assume that the type of the sporo-
gonium is essentially different from that of the lower Hepaticae,
and corresponds to that of the other Anthoceroteae. The
primary formation of the columella and the subsequent differ-
entiation of the archesporium occur elsewhere only in the
Sphagnaceae. From Notothylas, where the archesporium con-
stitutes the greater part of the older sporogonium, and the
columella and wall are relatively small, there is a transition
through the forms with a relatively large columella to Dendro-
ceros, where the spore formation is much more subordinated and
a massive assimilative tissue developed. In Notothylas the
secondary growth of the capsule at the base, while it continues
for some time, is checked before the capsule projects much
beyond its sheath. In Dendroceros the growth continues much

148

MOSSES AND FERNS

CHAP.

longer, although it does not continue so long as in Anthoceros.

The assimilative system of tissue in the latter is finally com-
pleted by the development of perfect stomata, and the growth

y^^^^-z

V THE ANTHOCEROTEjE 149

of the capsule is unlimited. All that is needed to make the
sporophyte entirely independent is a root connecting it with
the earth.

The Inter-relationships of the Hepaticce

From a review of the preceding account of the Liverworts,
it will be apparent that these plants, especially the thallose
forms, constitute a very ill-defined group of organisms, one set
of forms merging into another by almost insensible gradations,
and this is not only true among themselves, but applies also
to some extent to their connection with the Mosses and
Pteridophytes. The fact that the degree of development of
gametophyte and sporophyte does not always correspond makes
it very difficult to determine which forms are to be regarded as
the most primitive. Thus while Riccia is unquestionably the
simplest as regards the sporophyte, the gametophyte is very
much more specialised than that of Aneura or Sphcerocarpiis.
The latter is, perhaps, on the whole the simplest form we know,
and we can easily see how from similar forms all of the other
groups may have developed. The frequent recurrence of the
two-sided apical cell, either as a temporary or permanent con-
dition in so many forms, makes it probable that the primitive
form had this type of apical cell. From this hypothetical form,
in which the thallus was either a single layer of cells or with an
imperfect midrib like Sphcerocarpus^ three lines of development
may be assumed to have arisen. In one of these the differenti-
ation was mainly in the tissues of the gametophyte, and the
sporophyte remained comparatively simple, although showing
an advance in the more specialised forms. The evolution of
this type is illustrated in the germinating spores of the
Marchantiaceae, where there is a transition from the simple
thallus with its single apical cell and smooth rhizoids to the
complex thallus of the mature gametophyte. In its earlier
phases it resembles closely the condition which is permanent in
the simpler anacrogynous Jungermanniaceae, and it seems more
probable that forms like these are primitive than that they
have been derived by a reduction of the tissues from the more
specialised thallus of the Marchantiaceae. SpharocarpuSy
showing as it does points of affinity with both the lower
Marchantiaceae and the anacrogynous Jur^germanniaceae,
probably represents more nearly than any other known form

ISO MOSSES AND FERNS chap.

this hypothetical type. Its sporogonium, however, simple as it
is, is more perfect than that of Riccia, and if our hypothesis
IS correct, the Marchantiaceae must have been derived from
Sphcerocarpus-Wke, forms in which the sporophyte was still
simpler than that of existing species. Assuming that this is
correct, the further evolution of the Marchantiaceae is simple
enough, and the series of forms from the lowest to the highest
very complete.

In the second series, the Jungermanniaceae, starting with
Sp/uBTOcarpus, the line leads through Aneura^ Pellia, and similar
simple thallose forms, to several types with more or less per-
fect leaves — i.e. Blasia^ Fossombronia^ Treubia^ Haplomitrium,
These do not constitute a single series, but have evidently
developed independently, and it is quite probable that the
typical foliose Jungermanniaceae are not all to be traced back
to common ancestors, but have originated at different points
from several anacrogynous prototypes.

The systematic position of the Anthoceroteae is more
difficult to determine, and their connection with any other
existing forms known must be remote. While the structure of
the thallus and sporogonium in Notothylas shows a not very
remote resemblance to the corresponding structures in Sp/uero-
carpus^ it must be remembered that the peculiar chloroplasts of
the Anthoceroteae, as well as the development of the sexual
organs, are peculiar to the group, and quite different from other
Liverworts. To find chloroplasts of similar character, one must
go to the green Algae, where in many Confervaceae very similar
ones occur. It is quite conceivable that the peculiarities of the
sexual organs may be explained by supposing that those of
such a form as SpJicerocarpuSy for example, should become
coherent with the surrounding envelope at a very early stage,
and remain so until maturity. In Aneura we have seen that
the base of the archegonium is confluent with the thallus, in
which respect it offers an approach to the condition found in
the Anthoceroteae ; but that this is anything more than an
analogy is improbable. The origin of the endogenous anthcr-
idium must at present remain conjectural, but that it is
secondary rather than primary is extremely likely, as we know
that occasionally the antheridium may originate superficially.
In regard to the sporogonium, until further evidence is brought
forward to show that Notothylas may have the columella absent

V THE ANTHOCEROTEAl 151

in the early stages, it must be assumed that its structure in the
Anthoceroteae is radically different from that of the other
Liverworts. Of the lower Hepaticai Spfuerocarpus perhaps
offers again the nearest analogy to Notothylas^ but it would not
be safe at present to assume any close connection between the
two. Of course the very close relationships of the three genera
of the Anthoceroteae among themselves are obvious.

On the whole, then, thd evidence before us seems to indicate
that the simplest of the existing Hepaticae are the lower thallose
Jungermanniaceae, and of these Sphcerocarpus is probably the
most primitive. The two lines of the Marchantiaceae and
Jungermanniaceae have diverged from this common ancestral
form and developed along different lines. The Anthoceroteae
cannot certainly be referred to this common stock, and differ
much more radically from either of the other two lines than
these do from each other, so that at present the group must be
looked upon as at best but remotely connected with the other
Hepaticae, and both in regard to the thallus and sporophyte has
its nearest affinities among certain Pteridophytes. The possi-
bility of a separate origin of the Anthoceroteae from Coleochcete-
like ancestors is conceivable, but it seems more probable that
they have a common origin, very remote, it is true, with the
other Liverworts.

CHAPTER VI

THE MOSSES (MUSCI) : SPHAGNACEiE — ANDREiEACEiE

The Mosses offer a marked contrast to the Hepaticae, for while
the latter are pre-eminently a generalised group, the Mosses
with a very few exceptions are one of the most sharply-defined
and specialised groups of plants known to us. Although much
outnumbering the Liverworts in number of species, as well as
individuals, the differences in structure between the most extreme
forms are far less than obtain among the Liverworts. While
the latter occur as a rule in limited numbers, and for the most
part where there is abundant nioisture, the Mosses often cover
very large tracjts almost to the exclusion of other vegetation,
especially in northern countries. In more temperate regions,
the familiar peat-bogs are the best known examples of this
gregarious habit. * Mosses are for the most part terrestrial,
and are found in almost all localities. Some grow upon organic
substrata, especially decaying wood, and are to a greater or less
extent saprophytic. • Haberlandt ^ first called attention to this,
and investigated a number of forms, among them Rhynchostegiutn
muraley Eurynchium prcelongum^ Webera nutans^ and others, and
in these found that the rhizoids had the power of penetrating
the tissue of the substratum, much as a fungus would do. The
most remarkable case, however, is Buxbaumia, where the leaves
are almost completely absent and the saprophytic habit very
strongly pronounced. Most of the Mosses, however, are
abundantly provided with assimilative tissue, and grow upon
almost every substratum, although most of them are pretty
constant in their habitat. A number of species are typically
aquatic, />. Fontinalis and many species of Sphagnum and

1 Haberlandt (4),

W^"

CH.VI MOSSES {MUSCJ): SPHAGNACE^—ANDRE^ACEjE 153

Hypnum ; others grow regularly in very exposed situations on
rocks, e,g, Andreaa. Very many, like Funaria hygrometrica and
Atrickum undulatumy grow upon the earth ; and others again, like
species of Mnium and Thuidiunty seem to grow exclusively upon
the decaying trunks of trees. Indeed Mosses are hardly absent
from any lodalitj^ except salt water. With the exception of the
Sphagnaceae an'd Andre^aceae, and possibly Archidiunty the type
of structure foupd among, the Mosses is extraordinarily constant,
and they mky all be unhesitatingly referred to a single order,
the Bryaceae, which includes within it an overwhelming majority
of the species.

The gametophyte of the Musci always shows a well-marked
protonema, which in mo.st cases has the form of an extensively
branching alga-like filamentous structure^ from which later a
distinct leafy axis arises as a lateral bud. In Sphagnum this
protonema is a flat thallus, and the same is true. of Tetraphis
and a few other forms, but the filamentous protonema is very
much more common. The gametophore arises • from this
protonema as a lateral bud, which develops a pyramidal apical
cell, from which three sets of segments are cut off, each segment
developing a leaf. The only exception to this, so far as is
known at present, is the genus Fissidens} where the apical cell
is wedge-shaped, and only two sets of segments are formed.
Upon these leafy branches the sexual organs are borne. The
relative degree of development of the protonema and the game-
tophore differ much in different forms. Thus in the Phascaceae
the protonema is permanent, and the gametophore small and
poorly developed. In the higher ones, the protonema dis-
appears more or less completely, and the assimilative functions
are entirely assumed by the large highly developed gametophore,
which is capable of reproducing itself by direct branching
without the intervention of the protonema. The commonest
form of gametophore is the upright stem with the leaves
arranged radially about it, but in many creeping forms, such as
some species of Mniunty Hypnum^ etc., the gametophore is more
or less dorsiventral ; but in these the apical cell is pyramidal,
and produces three rows of leaves. Growing out from the base
of the stem in most Mosses, and fastening it to the substratum,
are numerous brown rhizoids which are not, however, morpho-
logically distinct from the protonema. Thus if a turf of growing

^ Leitgeb (2).

154 MOSSES AND FERNS chap.

Moss is turned upside down, the rhizoids thus exposed to the
light very soon develop chlorophyll, and grow out into normal
protonemal filaments.

In most of the Mosses the leaves show a one-layered lamina
traversed by a midrib, which may be quite small or very
massive. This midrib is made up in part of elongated thick-
walled sclerenchyma, and is obviously a conducting tissue.
The highest grade of development of the leaf is met with in
Polytrichum] where the midrib is very massive and peculiar
vertical laminae of chlorophyll-bearing cells grow out from the
surface of the leaf. In Buxbaumia the leaves are almost entirely
abortive. The peculiar leaves of Sphagnum will be referred to
later, as well as the details of structure of the leaves of other
forms.

The stem, except in the lowest forms, is traversed by a
well-defined central strand of conductive tissue, and in a few of
the highest ones, e,g, Polytrichum^ there are in addition smaller
bundles, continuations of the midribs of the leaves, recalling
the " leaf-traces " found in the stems of Spermaphytes.

The forms of non-sexual reproduction among the Musci are
extraordinarily various, and a careful study of them shows that
the morphological connection between the protonema and
gametophore is a very intimate one, as they may arise recip-
rocally one from the other. With the exception of certain
resting buds developed from the protonema it appears ^ that the
formation of the leafy stem is always preceded by the pro-
tonema. The latter arises primarily from the germinating
spores, but may develop secondarily from almost any part of
the gametophore or even in exceptional cases from the cells
of the sporophyte.^ From these protonemal filaments new
gametophores arise in the usual way. The gametophore itself,
especially where it is large and long lived, by the separaticy^ of
its branches rapidly increases the number of new individuals.
This is especially marked in Sphagnum^ where this is the
principal method of propagating the plants. Special organs
of propagation in the form of gemmae also occur, and these
may develop from the protonema or from the gametophore.
Tetraphis pelludda (Fig. ibj) is a good example, showing these
specialised gemmae which after a time germinate by giving rise
to a protonema upon which, as usual, the gametophore arises

* Goebel (lo), p. 170. ' Pringsheim (2) ; Stahl (i).

VI MOSSES {MUSCJ) : SPHA GNA CE^—ANDRE^A CEjE i 5 5

as a bud. In size the gametophore of the Mosses ranges from
a millimetre or less in height in Buxbaumia and Ephemerum
to 30 to 50 cm. in the large Polytrichaceae and Fontinalis.
The branching of the gametophore is never dichotomous, and so
far as is known the lateral branches arise, not in the axils of
the leaves, but below them. ' Underground stems or stolons,

Fig. ^l.—Climacium AtHtrkanum (Brid.), showing the formation of stolons, X2.

which afterwards develop into normal leafy axes, are common
in many forms, e,g, Climacium (Fig. 75).

The sexual organs are borne either separately or together
at the summit of the gametophoric branches. Where the
plants are dicecious, it sometimes happens that the two sexes
do not grow near together, in which case, although archegonia
may be plentiful, they fail to be fecundated and thus no cap-

156 MOSSES AND FERNS chap.

sules are developed. This no doubt accounts for the extreme
rarity of the sporogonium in many Mosses, although in other
cases, e,g, Spftagnum, it would appear that the formation of the
sexual organs is a rare occurrence. Thes^resemble in general
those of the Hepaticae, but differ in some of their details.
The leaves surrounding them are often somewhat modified,
and in the case of the male plants {Atrickum^ Polytrichutn)
different in form and colour from the other leaves, so that the
whole structure looks strikingly like a flower. As a rule, the
archegonial receptacles are not so conspicuous. The early
divisions of the archegonium correspond closely with those of .
the Liverworts, but after the " cover cell " is formed, instead of
dividing by cross walls into four cells, it functions for some
time as an apical cell, and to its activity is due the entire
development of the neck. The venter is usually very much
more massive than in the Hepaticae, and the egg small.

The antheridia, except in Sphagnum^ are borne alscr at the
apex of the stem, whose apical cell does not always, at any rate,
become transformed into an antheridiiim, as we sometimes find,
especially in species of Atrichum and Polytrichunty that the axis •
grows through the antheridial group and develops a leafy axis,
which later may form other antheridia at its apex. Where
the plants are dioecious the males are usually noticeably
smaller than the females. The antheridia, except in Sphagnum^
are very uniform in structure, and like the archegonium exhibit
a very definite apical growth (Fig, 90). The wall remains one-
layered, as in the Liverworts, and often the chloroplasts in its
cells become red at maturity, as in some Liverworts, e^.
Anthoceros. The ripe antheridium is in most Mosses club-
shaped, and the sperm cells are discharged while still in connec-
tion, the complete isolation of the sperm cells only taking place
some time after the mass has lain in water. In Sphagnum the
antheridia are much like those of certain leafy Liverworts, and
stand singly in the axils of the leaves of the male branches.

The sporogonium of the Mosses .reaches a high degree of
development in the typical forms, and shows great uniformity,
both in its development and in the essential structure of the
full-grown sporophyte. With the exception of Sphagnum^ which
will be referred to more specially later, the early growth of the
sporogonium is due to the segmentation of a two-sided apical
cell. The separation of the archesporium takes place at a late

VI MOSSES (AfC/SCI) : SPHA GNACE^—ANDREjEACEJE i 57

period,- and like that of Anthoceros it occupies but a very small
part of the sporogonium, which in all the higher forms attains
a considerable size and complexity. All the archesporial cells
form spores, and no trace of elaters can be found.

In all but the lower forms, the sporogonium becomes
differentiated into a stalk (seta) and a capsule. This differ-
entiation is gradual, and the elongation of the seta is not a
rapid process, due simply to an elongation of the cells, but is,
caused by actual growth and cell division. In Sphagnum and
Andreaa^ where no seta is present, the axis of the gametophore )
elongates and forms a sort of stalk (pseudopodium), which
carries up the capsule above the leaves.

The separation of .the capsule and seta takes place by a
rapid enlargement of the upper part of the very much elongated
embryo about the same time that the archesporium becomes
recognisable. This enlargement is accompanied by a separation
of the cells of two layers of the wall? by which an intercellular
space is formed which later may become very large (Figs.
97-100).. A second similar space may be formed inside the
archesporium, but this is found only in the Polytrichaceae. In
the Sphagnaceae and Andreaeaceae this space is not found.
These spaces are traversed by protonema-like filaments of
chlorophyll-bearing cells, and the cells of the massive wall of
the capsule also contain much chlorophyll, so that there is
no question that the sporogonium is capable of assimilation.
Stomata, much like those of Anthoceros or the vascular plants,
occur upon the basal part of the capsule in many species, but
are not always present.

In Sphagnum and all the higher Bryaceae the capsule opens
regularly by means of a circular lid or operculum. This in the
latter group is a most characteristic structure, and with its
accompanying structures, the " annulus " or ring of thickened
cells surrounding the opening of the rim, and the " peristome," —
the fringe of teeth inside the annulus, — form some of the most
important distinguishing marks of different genera and species.
When ripe, the operculum falls off and the ripe spores are set
free. The teeth of the peristome, by their hygroscopic move-
ments, play an important part in scattering the spores, and
physiologically take the place of the elaters of the Hepaticae.

Some Mosses live but a few months, and after ripening
their spores, die. This is the case with Funaria hygrometrica^

158 MOSSES AND FERNS chap.

at least in California. Other Mosses are perennial, and some
species of peat or tufa-forming Mosses seem to have an unlimited
growth, the lower portions dying and the apices growing on
until layers of peat or tufa of great thickness result, covered
over with the still living plants whose apices are the direct
continuation of the stems which form the basis of the mass.

With the exception of a very few forms all the Mosses are
readily referable to three orders. The first two, the Sphagnaceae
and the Andreaeaceae, are represented each by a single genus,
and are in several respects the forms that come nearest the
Liverworts. All the other Mosses, except perhaps Archidium
and Buxbaumiay conform to a very well-marked type of
development, and may be referred to a common order, the
Bryineae. The Phascaceae or cleistocarpous forms are sometimes
separated from the higher Bryineae as a distinct order, but a
study of their development shows that they belong to the same
series, and only differ in *Sthe degree of development from the
more specialised stegocarpous forms.

Order L Sphagnacem

The Sphagnaceae, or Peat-Mosses, are represented by the
single genus Spttagnum, They are Mosses of large size, which,
as is well known, often cover large tracts of swampy ^land and
about the borders of lakes, forming the familiar peat-bogs of
northern countries. Owing to the empty cells in the leaves and
outer layers of the stem, they suck up water like a sponge, and
the plants when growing are completely saturated with water.
The colour is usually pale green, but varies much in depth of
colour, and in many species is red or yellow. When dry the
colour is much duller, largely owing to the opacity of the dry,
empty cells which conceal to a great extent the colour of the
underlying tissues. They branch extensively, and, according to
Schimper, a branch is always formed corresponding to every
fourth leaf ; but Leitgeb has shown that although this is the
rule numerous exceptions to it occur. / In sterile plants the
branches are of two kinds, long flagellate branches which hang
down almost vertically and are applied to the stem, and much
shorter ones that are crowded together at the apex and have
only a limited growth. The leaves are inserted on the stem
by a broad base, and taper to a more or less well-marked point.

VI MOSSES (MUSCI) : SPHA GNA CE^—ANDRE^A CE^E 1 59

According to Schimper, the divergence of the leaves of the main
axis is always two-fifths, but on the smaller branches variations
from this sometimes occur. The leaves show no trace of a
midrib. As the axis elongates the leaves become separated, as

Fig. T^.—Sphagnum (j/); A, B, Young protonemata, X262; C, an older protonema with a leafy
bud (J^ X about 40 ; f , marginal rhizoids.

well as the lower branches, but upon the smaller branches they
remain closely imbricated. Root-hairs are present only in the
earlier stages of the plant's growth, and are only occasionally
found in a very rudimentary condition in the older ones.

The spores of Sphagnum on germination form first a very

i6o MOSSES AND FERNS chap.

short filament, which soon, at least when grown upon a solid
substratum, forms a flat thallus, which at first sometimes grows
by a definite apical cell.^ It first has a spatulate form (Fig.
76^ A, B), which later becomes broadly heart-shaped, and closely
resembles in this condition a young Fern prothalliu'm, for which
it is readily mistaken. The older ones become more* irregular
and may attain a diameter of several millimetres. The thallus
is but one cell thick throughout its whole extent, and is fastened
to the earth by colourless rhizoids. Later similar filaments
grow out from the marginal cells of the thallus, and a careful
examination shows that they are septate, and closely resemble
the protonemal filaments oif other Mosses. Like those, the
septa, especially in the colourless ones, are strongly oblique.
These marginal protonemal threads may, according to Hof-
meister^ and Schimper,® produce a flattened thallus at their
extremity, and thus the number of flat thalli may be increased.
Schimper states that if the germination takes place in water,
the formation of a flat thallus is suppressed and the protonema
remains filamentous, but Goebel disputes this.

In the few cases observed by me, only one leafy axis arose
from each thalloid protonema, and although this is not expressly
stated by Hofmeister and Schimper, their figures would indicate
it. At a point, usually near the base, a pro^berance is
formed by the active division of the cells, in a manner probably
entirely similar to that in other Mosses, and this rapidly assumes
the form of the young stem. The first leaves are very simple
in structure, and are composed of perfectly uniform elongated
quadrilateral cells, all of which contain more or less chlorophyll.
Like the older ones, however, they show the characteristic two-
fifth divergence. Schimper states that the fifth leaf, at the latest,
shows the differentiation into chlorophyll-bearing and hyaline
cells, found in the perfect leaves. The first leaves in which
this appears only show it in the tower part, the cells of the
apex remaining uniform.

At the base of the young plant very delicate colourless
rhizoids are developed, and these show the oblique septa so
general in the rhizoids of other Mosses. As the plant grows
older these almost completely disappear.

The apex of the stem and branches is occupied by a
pyramidal apical cell with a very strongly convex outer free
^ Goebel (12), p. 11. ' Hofmeister (i). • Schimper (i).

VI MOSSES {MUSCI): SPHAGNACEJE-ANDRE^ACE^ i6i

base. From the lateral faces of the apical cell, as in the
acrogynous Liverworts, three sets of segments are formed. The
whole vegetative cone is slender, especially in the smaller
branches. The first division in the young segment is parallel
to its outer face, and separates it into an inner cell, from which

A. B.

Fig. jt.— Sphagnum cymbi/olium (Ehrh.X A, Median longitudinal section of a slender branch ; jr,
the apical cell ; B, part of a section of the same farther down, showing the enlarged cells at the
liases of the leaves, and the double cortex if or) ; C, cross-section near the apex of a slender
branch ; D, glandular hair at the base of a young leaf— all X 525.

the central part of the axis is formed, and an outer cell which
produces the leaves and cortex.

The second wall, which is nearly horizontal, divides the
outer cells of the segment into an upper and a lower cell, the
former being much broader than the latter, which is mainly
formed from the kathodic half of the segment, which is higher
than the anodic half.^ The next wall divides the upper cell

* Leitgeb(i).
M

i62 MOSSES AND FERNS chap.

into an upper and a lower one, the former being the mother
cell of the leaf, the lower, with the other basal cell, giving rise
to the cortex. Growth proceeds actively in the young leaf,
which soon projects beyond the surface of the stem, and by the
formation of cell walls perpendicular to its surface forms a
laminar projection. The position of the cell walls in the young
leaf is such that at a very early period a two-sided apical cell
is established, which continues to function for a long time, and
to whose regular growth the symmetrical rhomboidal form of
the cells of the young leaf is largely due (Fig. 78). The leaves
do not retain their original three -ranked arrangement, but
from the first extend more than one-third of the circumference
of the stem, so that their bases overlap, and the leaves become
very crowded, and the two-fifth arrangement is established. The
degree to which the central tissue of the stem is developed
varies with the thickness of the branch. In the main stem it
is large, but in the small terminal branches it is much less
developed, as well as the cortex, which in these small branches
is but one cell thick. Later the cortex of the large branches
becomes two-layered (Fig. 77^ B), and is clearly separated from
the central tissue, whose cells in longitudinal section are very
much larger. In such sections through the base of very young
leaves characteristic glandular hairs are met with. They
consist of a short basal cell and an enlarged terminal cell
containing a densely granular matter, which from its behaviour
with stains seems to be mucilaginous. The form of the secret-
ing cell is elongated oval (Fig. 77^ D), and the hair is inserted
close to the base of the leaf, upon its inner surface.

The young leaf consists of perfectly uniform cells of a nearly
rhomboidal form (Fig. 78, A), and this continues until the apical
growth ceases. Then there begins to appear the separation
into the chlorophyll-bearing and hyaline cells of the mature
leaf. This can be easily followed in the young leaf, where its
base is still composed of similar cells, but where toward the
apex the two sorts of cells become gradually differentiated.
The future hyaline cells grow almost equally in length and
breadth, although the longitudinal growth somewhat exceeds
the lateral. These alternate regularly with the green cells,
which grow almost exclusively in length, and form a network
with rhomboidal meshes, whose interstices are occupied by the
hyaline cells. The latter at first contain chlorophyll, which

VI MOSSES (MUSCI) : SPHA GNA CE^—A NDRE^A CEAL 1 63

soon, however, disappears ; and finally, as is well known, they
lose their contents completely, and in most cases round openings

- B

5 I

are formed in their walls. The protoplasm is mainly used up
in the formation of the spiral and ring-shaped thickenings upon
the inner surface of the wall, so characteristic of these cells

1 64

MOSSES AND FERNS

CHAP.

(Fig. 78, D). The chlorophyll cells are sometimes so crowded
and overarched by the hyaline ones that they are scarcely
perceptible, and of course in such leaves the green colour is
very faint. Cross-sections of the leaves show a characteristic
beaded appearance, the large swollen hyaline cells regularly
alternating with the small wedge-shaped sections of the green
cells (Fig. 78, E). Russow^ has shown that the leaves of the
sporogonial branch retain more or less their primitive character,
and the division into the two sorts of cells of the normal leaves
is much less marked. He connects this with the necessity for
greater assimilative activity in these leaves for the support of
the growing sporogonium. From his account too it seems that
the stem leaves lose their activity very early.

The degree of development of the thickenings upon the
walls of the hyaline cells varies in different species, and in
different parts of the leaf It is, according to Russow,^ best
developed in the upper half of the leaf, where these thickenings
have the form of thin ridges projecting far into the cell cavity.

The development of the central tissue of the stem varies.
The central portion usually remains but little altered and
constitutes a sort of pith composed of thin-walled colourless
parenchyma, which merges into the outer prosenchymatous
tissue of the central region. The cells of the latter are very
thick walled, and elongated, and their walls are usually deeply
stained with a brown or reddish pigment. In their earlier
stages, according to Schimper,^ the prosenchyma cells have
regularly arranged and characteristic pitted markings on their
walls, but as they grow older and the walls thicken, these
become largely obliterated. Cross-sections of these prosen-
chyma cells show very distinct striation of the wall (Fig. yZ,
G), which becomes less evident as they approach the thinner-
walled parenchyma of the central part of the stem. No trace
of a central cylinder of conducting tissue, such as is found in
most of the Mosses, can be found in Sp/iagnufUy and this is
correlated with the absence of a midrib in the leaves.

The cortex at first forms a layer but one cell thick, but is
from the first clearly separated from the axial stem tissue. In
the smallest branches it remains one-layered (Fig. yy, C), but
in the larger ones it early divides by tangential walls into two
layers, which at this stage are very conspicuous (Fig. yj^ B).

' Russow (4). ^ Russow, Lc, p. 8. ' Schimper (1), p. 36.

VI MOSSES {MUSCI): SPHAGNACEAl— ANDRE JEACE^ 165

Later there may be a further division, so that the cortex of the
main axes frequently is four-layered. While the cells of the
young cortex are small, and the tissue compact, later there is
an enormous increase in size of the cells, which finally lose
their protoplasmic contents and resemble closely the hyaline
cells of the ' leaves. Like the latter, the cortical cells are
perfectly colourless, and usually have similar circular perfora-
tions in their walls. The resemblance is still more marked in
5. cymbifoliuniy where there are spiral thickened bands, quite
like those of the hyaline leaf cells. On the smaller branches
the cortical cells ^ have been found to be of two kinds — the
ordinary form and curious retort-shaped cells with smooth
walls and a single terminal pore.

The Branches

Leitgeb*^ has studied carefully the branching of Sphagnum,
which corresponds closely to the other Mosses investigated.
The branch arises from the lower of the two cells into which
the outer of the two primary cells of the segment is divided.
In this cell, which ordinarily constitutes part of the cortex, walls
are formed in such a way that an apical cell of the ordinary
form IS produced. These lateral branches themselves branch
at a very early period, and form tufts of secondary ones.
Schimper was unable to make out clearly what the nature
of this branching was, but suggested a possible dichotomy.
Leitgeb, however, concludes that it is monopodial, and that
each branch corresponds to a leaf, as do the primary branches.
The growth of all the lateral branches, both the descending
flagellate ones and the short upright ones at the top of the
stem, is limited, and lasts through one vegetative period only.
This, however, is not true of the branches that are destined to
contain the axis. These are apparently morphologically the
same as those whose growth is limited, but they continue to
grow in the same manner as the main axis.

The Sexual Organs

The sexual organs in Sphagnum are produced on branches
that do not differ essentially from the sterile ones. The leaves
of the antheridial branches are usually brightly coloured, — red,

* Schimper (i), p. 39. * Leitgeb (1).

i66

MOSSES AND FERNS

CHAP.

yellow, or dark green, and are closely and very regularly set,
so that the branch has the form of a small catkin (Fig. 79, A).

.-cal

Fig. 79.— a, Male catkin of Sphagnum cymH/oiium, x 50 ; B, young antheridiuni of S. tuuH/oUunt^
X 350 ; C, opened antheridium of the same species : D, spermatozoid, X 1000 (about) ; E, female
branch with sporogoninm of ^. acvti/oUuufy slightly magnified ; cal, calyptra. A, C, E, after
Schimper ; B, after Leitgeb.

The antheridia stand singly in the axils of the leaves, and
Leitgeb^ states that their position corresponds with that of

^ Leitgeb (4).

VI MOSSES {MUSCI): SPHAGNACE^—ANDRE.^ACE^ 167

branches, with which he regards them as homologous, having
observed in some cases a bud occupying the place of an
antheridium. He studied in detail their development, which
differs considerably from that of the other Mosses. The
antheridium arises from a single cell whose position corresponds
to that of a lateral bud on an ordinary branch. This cell
grows out into a papilla and becomes cut off by a transverse
wall. The outer cell continues to elongate without any
noticeable increase in diameter, and a series of segments are
cut off from the terminal cell by walls parallel to its base, so
that the young antheridium consists of simply a row of cells,
comparable to the very young antheridium of the Marchanti-
aceae. Intercalary transverse divisions may also arise, and
later some or all of the cells, except the terminal one, divide
by longitudinal walls, usually two intersecting ones in each cell,
so that the antheridium rudiment at this stage is composed of
a long stalk composed of several rows of cells, usually four,
and a terminal cell which later gives rise to the body of
the antheridium. The first divisions in the body of the
antheridium only take place after the stalk has become many
times longer than the terminal cell, and is divided into many
cells.

The account of the development of the antheridium given by
Hofmeister and Schimper is incomplete, and differs in some
respects from that of Leitgeb. Neither of the former observers
seems to have clearly recognised the presence of a definite
apical cell from the first. Schimper^ states that after the
stalk has been formed four rows of segments arise from the
terminal cell ; to judge from the somewhat vague statements of
Hofmeister^ it appears that he regarded the terminal growth
as taking place by the activity of a two-sided apical cell, as in
other Mosses. Leitgeb states that, while this form of growth
does frequently occur, usually the divergence of the seg-
ments is not exactly half, and the segments do not stand in
two straight rows, but some of them are intercalated be-
tween these, forming an imperfect third row. Each segment
is first divided by a radial wall into nearly equal parts, and
these are then divided into an outer and an inner cell, and from
the latter by repeated divisions the sperm cells are formed.
The body of the full-grown antheridium is broadly oval, and

* Schimper (i), p. 45. ^ Hofmeister (i), p. 154-

i68

MOSSES AND FERNS

CHAP.

both in its position and shape recalls strongly that of such
a foliose Liverwort as Porella,

The development of the spermatozoids has been carefully
followed by Guignard/ and corresponds in the main with that
of the Hepaticae. A peculiar feature is the presence of a pear-
shaped amylaceous mass, firmly attached to the posterior coil.
This becomes evident at a very early stage in the development
and remains unchanged up to the time the spermatozoids are
liberated (Fig. 79, D). The vesicle in which it is enclosed
collapses, leaving only the large starch granule, which finally
becomes detached. The free spermatozoid has about two com-
plete coils, and in form recalls that of Chara. The cilia are
two and somewhat exceed in length the body.

The ripe antheridium is surrounded by a weft of fine
branching hairs, which Schimper suggests serve to supply it
with moisture.^ It opens by a number of irregular lobes (Fig.
79, C), precisely as in Porella, and, like that, the swelling of the
cells is often so great that some of them become entirely
detached. Schimper states that antheridia may be formed at
any time, but they are more abundant in the late autumn and
winter.

The archegonia are found at the apex of some of the
short branches at the summit of the plant, and externally are
indistinguishable from the sterile branches. The development
of the archegonia has not been followed completely, but to
judge from the stages that have been observed and the mature
archegonium, its structure and development correspond closely
to that of the other Mosses. As in these, and the acrogy-
nous Hepaticae, the apical cell of the branch becomes an arche-
gonium, and a varying number of secondary archegonia arise
from its last - formed segments. The mature archegonium
has a massive basal part and long somewhat twisted neck,
consisting of six rows of cells. As in the other Mosses, the
growth of the young archegonium is apical, and probably as
there the neck canal cells are formed as basal segments of
the apical cell, and the ventral canal cell is cut off from the
central cell in the usual way. The venter merges gradually
into the neck above and the pedicel below, and at maturity
its wall is two or three cells thick. The egg ^ is ovoid, and

* Guignard (i), p. 69.

* These are probably the hyphae of a fungus.
» Waldner (2).

VI MOSSES {MUSCI): SPHAGNACEAL—ANDREA^ACE^ 169

the nucleus shows a distinct nucleolus. Whether a receptive
spot is present is not stated. Mixed with the archegonia are
numerous fine hairs like those about the antheridium. The
leaves immediately surrounding the group of archegonia later

Fig. Zo,— Sphagnum acutifolium (Ehrh.). Development of the embryo (after Waldncr). A-D,
Median optical section : E, F, cross-sections. A, D, E, F, X360; C, X315 ; D, XX53.

enlarge much and form a perichaetium. By the subsequent
elongation of the main axis both archegonial and antheridial
branches are often separated by the growth of the axis
between them, although at first they are always crowded
together at the top of the main stem.

I70 MOSSES AND FERNS chap.

The Sporogonium

Waldner^ has recently studied carefully the development
of the embryo of Spltagnum^ yAi\<Ai differs essentially from all
the other Mosses, and has its nearest affinity in the Antho-
ceroteae. In the species 5. acutifolium^ mainly studied by
Waldner, the sexual organs are usually mature in the late
autumn and winter, and fertilisation occurs early in the spring.
The ripe sexual organs are found in a perfectly normal condi-
tion in mid-winter, under the snow, and apparently remain in
this condition until the first warm days, when they open and
fertilisation is effected. The first embryos were found late in
February, and development proceeded from that time.

The first division in the embryo is horizontal and divides it
into two cells. In the lower of these the divisions are irregular,
but in the upper one the cell walls are arranged with much regu-
larity. The upper cell is the apical cell of the young embryo,
and from it, by walls parallel to the base, a series of segments is
formed (Fig. 80, A). These are usually about seven in number,
and each of these segments undergoes regular divisions, these
beginning in the lower ones and proceeding towards the apical
cell, which finally ceases to form basal segments and itself
divides in much the same way as the segments. The latter
first divide by two vertical divisions into quadrants, and in each
quadrant either directly by periclinal walls, or by an anticlinal
wall followed by a periclinal wall in the inner of the two cells
(Fig. 80, E), four central cells in each segment are separated
from four or eight peripheral ones. The terms endotheciunt
and antphithecium have been given respectively to these two
primary parts of the young Moss-sporogonium. By the time
that the separation of endothecium and amphithecium is com-
pleted, a division of the embryo into two regions becomes
manifest (Fig. 80, C). Only the three upper segments, in-
cluding the apical one, give rise to spores ; the lower segments
together with the original basal cell of the embryo form the
foot, which in Spliagnum is very large. The cells of the foot
enlarge rapidly and form a bulbous body very similar in
appearance and function to that of Notothylas or AntJioceros,
The next divisions too in the upper part of the sporogonium

1 Waldner {2).

VI MOSSES {MUSCI): SPHAGNACE^—ANDRE^ACE^ 171

find their nearest analogies in these forms. The central mass
of cells, both in position and origin, corresponds to the
columella in these genera, and the archesporium arises by the
division of the amphithecium into two layers by tangential
walls, and the inner%f these two layers, in contact with the
columella, becomes at once the archesporium. By rapid cell
division the upper part of the sporogonium becomes globular,
and is joined to the foot by
a narrow neck, much as in
Notothylas (Fig. 81). The
single - layered wall of the
young sporogonium becomes
six or seven cells thick, and
the columella very massive.
The one -layered archespor-
ium also divides twice by
tangential walls, and thus is
four-layered at the time the
spore mother cells separate.
All the cells of the arche-
sporium produce spores of
the ordinary tetrahedral form.
The so-called " microspores "
have been shown conclu-
sively to be the spores of a
parasitic fungus.' ' The layer
of cells in immediate contact
with the archesporium on
both inner and outer sides

has more chlorophyll than Fig. Si.— Median longitudinal section of a nearly

the neighbouring cells, and r\^ ^v^ow^^,r^ois.<uuti/oHun.,'K^,' ps.

^ o » pseudopodium ; f/, spores ; col^ columella (after

forms the " spore-sac." waidncr).

The ripe capsule opens
by a circular lid which is indicated long before it is mature.
The epidermal cells where the opening is to occur grow less
actively than their neighbours, and thus a groove is formed
which is the first indication of the operculum. The cells at
the bottom of the groove have thinner walls than, the
other cells of the capsule wall, and when it ripens these
dry up and are very readily broken, so that the operculum

^ Nawnschin ( i ).

172

MOSSES AND FERNS

CHAP.

is very easily separated from the dry capsule. Stomata,
according to Schimper/ always are present, sometimes in
great numbers ; but Haberlandt ^ states that these are always
rudimentary', and he regards them as reduced forms. No seta
is formed, but its place is taken physiorogically by the upper
part of the axis of the archegonial branch, which grows up
beyond the perichaetium, carrying the ripe sporogonium at its
top (Fig. 79, E). The upper part of this " pseudopodium " is
much enlarged, and a section through it shows the bulbous fcx>t
of the capsule occupying nearly the whole space inside it. The
ripe capsule breaks through the overlying calyptra, the upper
part of which is carried up somewhat as in the higher Mosses,
while the basal part together with the upper part of the pseudo-
podium forms the " vaginula."

The disorganised contents of the canal cells, which are
usually ejected from the archegonium, in Sphagnum remain in
a large measure in the central cavity, and on removing the
young embryo from the venter of the archegonium, this muci-
laginous mass adheres to it and forms a more or less complete
envelope about it, in which are often found the remains of
spermatozoids.

The species of Sphagnum are either monoecious or dioecious,
but in no cases do archegonia and antheridia occur upon the
same branch.

The Andreceacece

The second order* of the Mosses includes only the small
genus Andrecea^ rock-inhabiting Mosses of small size and dark
brown or blackish colour. In structure they are intermediate
in several respects between the Sphagnaceae and the Bryineai,
as has been shown by the researches of Kiihn ^ and Waldner/
to whom we owe our knowledge of the life-history of Andreaa.
They all grow in dense tufts upon silicious rocks, and are at
once distinguished from other Mosses by the dehiscence of
their small capsules. These, like those of Sp/iagnum, are raised
upon a pseudopodium, but are destitute of a true seta. The
capsule opens by four vertical slits, which do not, however,
extend entirely to the summit (Fig. 82). This peculiar form
of dehiscence recalls the Jungermanniaceae, but is probably only

^ Schimi>er (i), p. 55. ^ Haberlandt (4), p. 475. ' KUhn (l).

* Waldner (2).

VI MOSSES (MUSCI): SPHAGNACE^—ANDRE.EACE.-E 173

an accidental resemblance. The closely-set stems branch freely ;
the leaves, with three-eighth divergence, are either with a mid-
rib {A, rupestris) or without one {A, petrophila).

The growth of the stem is from a pyramidal apical cell, as
in Sphagnum^ and pftbably the origin of the branches is also
the same as in that genus. The growth of the young leaves is
usually from a two-sided apical cell, but another type of growth

Fig. 82. — Andrteea petropkila {JL\ix\i.\ A, Plant with ripe sporogonium, x lo ; B, median
section of nearly ripe capsule, X 80 ; ps^ pseudopodium ; col^ columella.

is found where the apical cell is nearly semicircular in outline,
and segments are cut off from the base only. These two forms
of apical growth apparently alternate in some instances in the
same leaf. The originally thin walls of the leaf cells later
become thick and dark -coloured, whence the characteristic dark
colour of the plant.

The stem in cross-section shows an almost uniform struc-
ture, and no trace of the central conducting tissue of the higher
Mosses can be found. The outer cells are somewhat thicker-
walled and darker-coloured, but otherwise not different from

174

MOSSES AND FERNS

the central ones. Numerous rhizoids of a peculiar structure
grow from the basal part of the stem, and from these, new
branches arise which replace the older ones as they die away.
These rhizoids are not simple rows of cells as in the Bryineae,
but are either cylindrical masses of celft or flattened plates.
These penetrate into the crevices of the rocks, or apply them-
selves very closely to the surface, so that the plants adhere
tenaciously to the substratum.

Scores and Protonema

The germination of the spores and the development of
the protonema show numerous peculiarities. The spores may

A B

Fiii. 83.— A, K, Germinating spores of W./r/n>/A//rt, X200; C, protonema with bud (Xr) ; D, >ounf(
archegonium in optical section ; E, i, 2, two views of a very young embryo of A. crassintrtay
X 366 ; F, somewhat older embryo of /I. petrophila ; G, older embryo showing the first archesporial
cells; H, I, cross-sections of young embryos, X200. A-D, after Kilhn ; E-I, after Waldner.

germinate within a week, or sometimes remain unchanged for
months. They have a thick dark-brown exospore and contain
chlorophyll and oil. The first divisions take place before the
exospore is ruptured, and may be in three planes, so that the
young protonema then has the form of a globular cell mass
(Fig. 83, A). This stage recalls the corresponding one in
many of the thallose Hepaticae, e.g'. Pellia, Radula, and is
entirely different from the direct formation of the filamentous
protonema of most Mosses. Some of the superficial cells of
this primary tubercle grow out into slender filaments, either
with straight or oblique septa, and these later ramify exten-

VI MOSSES {MUSCI): SPHAGNACE.^—ANDRE^ACE.E 175

sively. Where there are crevices in the rock, some of these
branches grow into them as colourless rhizoids, but here, as in
the Bryineae, there is no real morphological distinction between
rhizoid and protonema. Most of the filamentous protonemal
branches do not remain in this condition, but become trans-
formed into cell plates or cylindrical cell masses, like the stem-
rhizoids. The flat protonema recalls strongly that of Sphagnum ^
and is probably genetically connected with it. All of the
different protonemal forms, except what Kiihn calls the " leaf-
like structures," vertical cell surfaces of definite form, can give
rise to the leafy axes. The development of these seems to
correspond exactly with that of the other Mosses, and will not
be further considered here.

Tlie Sexual Organs

The species of Andrecea may be either monoecious or
dicEcious. Archegonia and antheridia occur on separate
branches, but their origin and arrangement are identical. The
first-formed antheridium develops directly from the apical cell
of the shoot, and the next older ones from its last-formed
segments, but beyond this no regularity can be made out. In
the first one the apical cell projects, and its outer part is
separted from the pointed inner part by a transverse wall.
This is followed by a second wall parallel to the first, so that
the antheridium rudiment is composed of three cells. Of these
the lower one takes little part in the future development. Of
the two upper cells the terminal one becomes the body of the
antheridium, the other the stalk. In the former, by two inclined
walls, a two-sided apical cell is developed, and the subsequent
growth is the same as in the Bryineae. The middle cell of the
antheridium rudiment divides repeatedly by alternating trans-
verse and longitudinal walls, and forms the long two-rowed
stalk of the mature antheridium. On comparing the antheridium
with that of the other Mosses, we find that it approaches
Sp/iagnum in the long stalk, but in its origin and the growth
of the antheridium itself, it resembles closely the higher Mosses.

The first archegonium also is derived immediately from the
apical cell of the female branch, and the first divisions are the
same as in the first antheridium. Here, too, the subsequent
development corresponds exactly with that of the higher

176

MOSSES AND FERNS

Mosses, and will be passed over for the present. The ripe
archegonium shows no noteworthy peculiarities, and closely
resembles in all respects that of the other Mosses.

The Sporogonium

The more recent researches of Waldner ^ on the develop-
ment of the sporogonium of Andrecea have shown clearly that
here, too, the latter stands between the Sphagnaceae and the
Bryineae. The first division in the fertilised ovum is transverse
and divides it into two nearly equal parts. The lower of these
divides irregularly and much more slowly than the upper one.
In the latter (Fig. 83, E) the first division wall is inclined, and
is followed by a second one which meets it nearly at right
angles, and by walls inclined alternately right and left — in
short, has the character of the familiar " two-sided " apical cell.
The number of segments thus formed ranges from eleven to
thirteen. Each segment is first divided by a vertical median
wall into equal parts, so that a cross -section of the young
embryo at this stage shows four equal quadrant cells. The
next divisions correspond to those in Sphagnum, and result in
the separation of the endothecium and amphithecium. The
formation of the archesporium, however, differs from Sphagnum^
and is entirely similar to that of the higher Mosses. Instead
of arising from the amphithecium as in the former, the arche-
sporium here is formed by the separation of a single layer of
cells from the outside of the endothecium. All of the segments
do not form spores, but only three or four, beginning with the
third from the base. The two primary segments of the upper
part of the embryo, like the corresponding ones in Sphagnum^
go to form the foot, which is not so well developed, however,
as in the latter. The originally one-layered archesporium later
becomes double, and as in Sphagnum extends completely over
the columella, which is thus not continuous with the tissue of
the upper part of the sporogonium. As in Sphagnum also, no
trace of the intercellular space formed in the amphithecium of
the Bryineae can be detected. A section of the nearly ripe
capsule shows the club-shaped columella extending nearly to
the top of the cavity. With the growth of the capsule the

^ Waldner (2).

VI MOSSES {MUSCI) : SPHA GNACEM—ANDRE.^A CE^E 1 77

space between the inner and outer spore -sacs becomes very
large to accommodate the growth of the numerous spores.
The pseudopodium is exactly the same as in Sphagnum^ and
the vagtnula and calyptra are present. The latter is much
firmer than in Sphagnum, and Hke that of the Bryinese*

Arckidium

The genus Arckidium is one whose systematic position has
beeti long a subject of controversy. It has usually been associated

Fj<?» %i^^Ar^hidmm JiiovM^fii (Aust.). A, M^ian sectian through a neAHy ripe spoo-ogfafrticun,
>i^; l^f bnne ckT the spom^cxnlitnit XaTa

with the so-called cleistocarpous Bryinea;, but the researches of
Leitgeb seem to point to a nearer affinity with Andremi.

The species of Arckidium arc small Mosses growing on the
earth, and especially characterised by the small number, but
very large size, of the spores contained in the sessile globular
sporogonium, Hofmclster ^ was the first to study the develop-

' Mofmeisier (1)1 p^ i6q*
N

178

MOSSES AND FERNS

ment, and his account agrees in the main with Leitgeb's,^
except as to the relation of the colunxella and outer spore-sac.
The first divisions in the embryo correspond exactly to those
in Andrecea and the Bryineae, and for a time the young embryo
grows from a two-sided apical cell. The secondary divisions
in the segments, however, are quite different from that observed
in any other Moss, and are like those in the antheridium.
Instead of the first wall dividing the segment into equal parts,
it divides very unequally. The second wall strikes this so as
to enclose a central cell, triangular in cross-section, which with
the corresponding cell of the adjacent segment forms a square.
This square, the endothecium, does not therefore at first show
the characteristic four-celled stage found in all other Mosses.
The amphithecium becomes ultimately three-layered, and be-
tween the second and third layers an intercellular space is
formed, as in the Bryineae, but this extends completely over the
top of the columella. The most remarkable feature, however,
is that no archesporium is differentiated, but any cell of the
endothecium may apparently become a spore mother cell. The
number of the latter is very small, seldom exceeding five or six. /
They become rounded off, and gradually displace the other
endothecial cells, which doubtless serve as a sort of tapetum for
the nourishment of the growing spores. Each spore mother
cell as usual gives rise to four spores, which are here very much
larger than in any other Moss. A section of the ripe sporo-
gonium (Fig. 8i) shows that only one of the primary three
layers of amphithecial cells can be recognised except at the
extreme apex and base. The seta is present, and a foot, much
like that of Aftdrecea, and penetrating into the tissue of the
stem apex, is seen.

Leitgeb is inclined to look upon Archidiunt as a primitive
form allied on the one hand to Andrecea and on the other to
the Hepaticae, possibly Notothylas, However, as his assumption
that the latter has no primary columella has been shown to be
erroneous, his comparison of the whole endothecium oiArchidium
with that of Notothylas cannot be maintained, as we have shown
that in the latter, as in Anthoceros^ the archesporium arises from
the amphithecium, and not from the endothecium, as is the case
in Archidiunt. Inasmuch as the gametophyte and sexual
organs of Archidium are those of the typical Mosses, it seems

» Leitgeb (8).

VI MOSSES (MUSCI) : SPHA GNA CE^E—ANDRE^A CE^ 1 79

quite as likely that the older view that Archidium is a degenerate
form is correct. At any rate, until more convincing evidence
can be brought forward in support of a direct connection between
it and the Hepaticae than the formation of the spores directly
from the central tissue of the sporogonium, it cannot be said
that the question of its real affinities is settled.

CHAPTER VII

THE BRYINE^

Under the name Bryineae may be included all the other
Mosses ; for although the so-called cleistocarpous forms are
sometimes separated from the stegocarpous Mosses as a special
order, the Phascaceae, the exact correspondence in the develop-
ment of both the gametophyte and sporophyte shows that the
two groups are most closely allied, the former being either
rudimentary or degraded forms of the others.

With few exceptions the protonema is filamentous and
shows branches of two kinds, the ordinary green ones with
straight transverse septa, and the brown-walled rhizoids with
strongly oblique ones, but the two forms merge insensibly into
one another, and are mutually convertible. In a few fomas,
notably the genus Teiraphis^ the protonema is thalloid, and as
in Sphagnum these flat thalli give rise to filamentous protonemal
threads, which in turn may produce secondary thalloid proto-
nemata. In some of the simpler forms, e,g. Ephemerum, the
protonema is permanent, and the leafy buds appear as append-
ages of it ; but in most of the larger Mosses the primary
protonema only lives long enough to produce the first leafy
' axes, which later give rise to others by branching, or else by
secondary protonemal filaments growing from the basal rhizoids.
The early stages of development of the primary protonema are
easily traced, as the spores of most Mosses germinate readily
when placed upon a moist substratum. The ripe spores usually
contain abundant chlorophyll and oil, and the thin exospore is
brown in colour. The spore absorbs water and begins to
enlarge until the exospore is burst, when the endospore pro-
trudes as a papilla which grows out into a filament ; or the

CHAP. VII

THE BRYINEA^

i8i

endospore sometimes grows out in two directions, and one of
the papillae remains nearly destitute of chlorophyll and forms
the first rhizoid. The growth of the protonemal filaments is
strictly apical, no intercalary divisions taking place except those
by which lateral branches arise. If abundant moisture is
present, the protonema grows with great rapidity and may form
a dense branching alga -like growth of considerable extent.
Sooner or later upon this arise the leafy gametophores. The
development of the latter, as we have seen, also takes place

^=^

Fig. 85. — Fuftaria hygromeirica (Sibth.). A, Fragment of a protonemal branch with a young game-
tophoric bud ; r, rhizoid ; B, median optical section of the bud ; C, older bud — i, surface view ;
3, optical section ; x^ apical cell ; D, protonema with a still older gametophore ig^n/n) attached.
AC, X225; D, X36.

abundantly from the secondary protonemal filaments which may
be made to grow from almost any part of the gametophore.

The development of the bud is as follows. From a cell of
the protonema a protuberance grows out near the upper end.
This is at first not distinguishable from a young protonemal
branch, but it very soon becomes somewhat pear-shaped, and .
instead of elongating and dividing simply by transverse walls,
the division walls intersect so as to transform it into a cell mass.
After the cell is separated it is usually divided at once by a .

1 82

MOSSES AND FERNS

CHAP.

strongly oblique wall, which is then intersected by two others
successively formed and meeting each other and the first-formed
one at nearly equal angles, so that the terminal cell of the
young bud (Fig. 85, A) has the form of an inverted pyramid ;
that is, by the first divisions in the bud the characteristic
tetrahedral apical cell of the gametophore is established. From
now on the apical cell divides with perfect regularity, cutting
off three sets of lateral segments. From the base of the young
gametophore the first rhizoid (Fig. 85, A, r) is formed at a very
early period. The first two or three segments do not give rise
to leaves, and the leaves formed from the next younger segments
remain imperfect. Thus in Funaria hygrometrica these earliest
formed leaves show no midrib. The young leaves rapidly
elongate and completely cover up the growing point of the
young bud^ and are at first closely imbricated. Later, by the
elongation of the axis, the leaves become more or less completely
separated (Fig. 85, C, D). In Funaria, as well as in many
other Mosses, buds are often met with that have become arrested
in their development, lost their chlorophyll, and assumed a dark-
brown colour. This arrest often seems to be the result of un-
favourable conditions of growth, and under proper conditions
these buds probably always will develop either directly or by
the formation of a secondary protonema into perfect plants.

Apical Growth of tlie Stem

The growth of the stem of the fully-developed gametophore
is better studied in one of the larger Mosses. The growth of
the gametophore is so limited in length in Funaria that it is
not so well adapted for this. Perhaps the best species for this
purpose is the well-known Fontinalis antipyretica, which has
already been carefully studied by Leitgeb.^ Amblystegium
riparium, var, fluitans, was examined by me and differed in
some points from Leitgeb's figures of Fontinalis, Fig. 86, A
shows an exactly median longitudinal section through a strong
growing point. Compared with Leitgeb's figures the apical cell
is much deeper than in Fontinalis, and in consequence the young
segments more nearly vertical. Here, as in Sphagnum, the first
wall in the young segment divides it into an inner and an outer

1 Leitgeb(i).

VII

THE BRYINEjE

183

cell, from the latter of which alone are formed the lateral
appendages of the stem. The inner cells of the segments by
repeated longitudinal and transverse divisions form all the tissues
of the axis. The second division wall in the segment, like that
in Sphagnum, is at right angles to the first, but in Atnblystegium
it extends the whole breadth of the segment. By this division
the outer of the two primary cells of the segment is divided
into an upper cell, from which the leaf develops, and a lower
one, from which the outer part of the stem and the buds are

Fig. 86. — A mbiysteg^ium ripariunt^ var.fluitans (Bruch and Schimp). A, Median longitudinal section
of a strong shoot ; Xy apical cell ; jr', initial of a lateral branch, X 350 ; B, transverse section
through the apex, X 250 ; C, similar section through a young branch, X 500.

formed. The leaves grow from a two-sided apical cell (Fig. 87),
as indeed they seem to do in all Mosses, and the divisions pro-
ceed with great rapidity and the young leaves quickly grow
beyond and surround the growing point. In Amblystegium, as
in all the typical Bryineae, the leaf has a well-developed midrib.
The formation of this begins while the leaf is very young and
proceeds from the base. In the middle row of cells (Fig. 87, C)
a wall first arises parallel to the surface of the leaf, and this is
followed by a wall in the cell on the lower side of the leaf

1 84

MOSSES AND FERNS

(Fig. 87, D). By further divisions in all the cells of this central
strand the broad midrib found in the mature leaf is developed.
In Aniblystegium all the cells of the midrib are alike and have
thickened walls. The midrib projects on both sides of the leaf,
but rather more strongly upon the lower side. In Funaria
(Fig. 88) the structure of the midrib is more definite. Here
two rows of cells take part in the formation of the midrib.
Each of these first divides as in Amblystegiuni by a wall parallel
to the surface of the leaf, so that in cross-section the central

Fig. 87. — Amblystegium ripariuin, var. Jiuitansi^r. and Sch.). A, Longitudinal section of the stem
passing through a young lateral branch (Jk) ; A, hair at the base of the subtruding leaf ; B, hori-
zontal section of a very young leaf, showing the apical cell {x) ; C, D, transverse sections of young
leaves, showing the development of the midrib. All the figures X 525,

part of the leaf shows a group of four cells, those on the outer
side being larger than the others. In the former the next wall
is a periclinal one and divides the cell into an inner and an
outer one. From the two inner cells by further division is
formed the group of small conducting cells that traverse the
centre of the midrib, while the outside cells together with those
on the inner side of the midrib become much thickened and
serve for strengthening the leaf. Here as in Amblystegium the
lamina of the leaf remains single-layered, and its cells contain
numerous large chloroplasts which, as is well known, continue

THE BRYINE^

i8s

to multiply by division after the cells are fully grown. The
marginal cells in the leaf of Funaria are much narrower than
those between them and the midrib, and their forward ends

Fig. 88. — Funaria kygrom^trica (Sibth.). A, Transverse section of the apex of a young shoot, x 515 ;
B, C, cross-sections of young leavet, XS15 ; D, cross-section of the stem, X357.

often project somewhat, giving the margin of the leaf a serrate
outline, which is also common in many other Mosses.

The Branches

For the study of the branching of the stem, Aniblystegium
again is much better than Funaria^ whose short stem and
infrequent branching make it difficult to find the different
stages. In Amblystegiunt^ however, every median section will
show some of the stages, and it is easy to follow out all the
details, as has already been done in Fontinalis by Leitgeb.^
The lateral shoots originate from a basal cell of the segment
below the middle of the leaf. It is very easily seen that it

1 Leitgeb (i).

i86

MOSSES AND FERNS

CHAP.

belongs to the same segment as the leaf standing above it, and
therefore is not axillary in its origin. The mother cell of the
young branch projects above the surrounding cells, and in it
are formed in succession three oblique intersecting walls which
enclose the narrow pyramidal apical cell (Figs. 86, 87). The
secondary divisions in the first set of segments are not so
regular as in the later ones, but the bud rapidly grows, and
very soon the perfectly regular divisions of the young segments
are established. So far as investigations have been made upon
other genera, they follow the same line of development as
Amblystegium^ Fonttnalis, and Sphagnum.

Where the growth of the main axis is stopped by the
formation of sexual organs, a lateral branch frequently grows
out beyond the apex of the main axis, as in Sphagnum, and
thus sympodia arise. In other cases, where the growth of the
lateral branches is limited, characteristic branch systems arise,
such as we find in Thuidium or Climacium (Fig. 75).

Compared with Amblystegium, the growing point of Funaria
and other Mosses of similar habit is much broader, and the
apical cell not so deep. The arrangement of the segments is
much the same, except that the original three-ranked arrange-
ment of the segments which is retained in Fontinalis ^ is replaced
in most Mosses by a larger divergence, owing to a displacement
like that in Sphagnum,

A cross-section of the older stem (Fig. 88, D) shows in
most Bryineae a central cylinder of small thin - walled cells
surrounded by a large-celled cortical tissue, which in the older
parts of the stem often has its walls strongly thickened and
reddish brown in colour. An epidermis, clearly recognisable
as such, cannot usually be detected. The outer cells contain
chlorophyll, which is wanting in the central cylinder.

The rhizoids in Funaria grow mainly from the base of the
stem, and the first ones arise very soon after the young bud is
formed. Their growth, like that of the protonemal branches,
is strictly apical, and they branch extensively. The young
ends are colourless, but as they grow older the walls assume a'
deep brown colour. Usually the division walls in the rhizoids
are strongly oblique. Their contents include more or less oil,
and where they are exposed to the light, chlorophyll.

* This is only strictly true in the smaller branches.

THE BR VINE ^

187

The Sexual Organs

Funaria is strictly dioecious. The male plants (Fig. 89, A)
are easily distinguished by their form. They are about i cm.

in height, with the lower leaves scattered, but the upper ones
crowded so as to present much the appearance of a flower whose
centre forms a small reddish disc. These male plants either
grow separately or more or less mixed with the females.

1 88

MOSSES AND FERNS

CHAP.

Whether the first antheridium, as in Andrecea and Fontinalis,
arises from the apical cell is doubtful, and it is impossible to
trace any regularity in the order of formation of the very
numerous antheridia. Except in very old plants, all stages
of development are found together, and the history of the
antheridium may be easily followed. A superficial cell projects
above its neighbours, and this papilla is cut off by a transverse

Fig. qQ.—Funaria hygrometrica (Sibth.). Development of the antheridium. A-D, Longitudinal
section;, of young stages, X 600 ; D is cut in a plane at right angles to C ; E, optical section of
an older stage, X 300 ; G, F, cross-sections of young antheridia, X 600 ; H, diagram showing the
first divisions in the antheridium ; I, young spermatozoids, X laoo.

wall. The outer cell either becomes at once the mother cell of
the antheridium, or other transverse walls may occur, so that a
short pedicel is first formed (Fig. 90, A). Finally in the
terminal cell, as in Andreceay two intersecting walls are formed
enclosing a two-sided apical cell, from which two ranks of
segments are cut off in regular succession (Figs. A, B, C). The
number of •these segments is limited, in Funaria not often
exceeding seven, and after the full number has been formed, the

^'•:;^'T7^5f"-'

THE BR VINE ^

189

apical cell is divided by a septum parallel with its outer face
into an inner cell, which with the inner cells of the segments
forms the mass of sperm cells, and an outer cell which produces
the upper part of the wall. Before the full number is com-
pleted, the secondary divisions begin, proceeding from the base
upward. These are very regular, and correspond closely to
those in the antheridium of the Jungermanniaceae, and can
only be clearly made out by comparing transverse and verti-
cal sections of the young antheridium. Fig. 90, H shows a
diagram illustrating this : i is the wall separating two adja-
cent segments, and 2 the first wall formed in the segment
itself The wall 2, it will be seen, starts near the middle of the
periphery of the segment and strikes the wall i far to one side
of the centre, so that the segment is thus divided into two cells
of very unequal size, although their peripheral extent is nearly
equal. The next wall (3) strikes both the wall i and 2 at
about equal distances from the periphery, and thus each
segment is divided into an inner cell which in cross-section has
the form of a triangle, and two peripheral cells. The latter
divide only by radial walls, and give rise to the single-layered
wall of the antheridium. The inner cells of the segments by
further division in all directions form the mass of sperm cells.
The first division wall in the central cell starts from near the
middle of the segment wall and curves slightly, so that the two
resulting cells are unequal in size. From this first division
wall usually two others having a similar form extend to the
peripheral cells, and these are next followed by others nearly at
right angles to them. After this transverse and longitudinal
walls succeed with such regularity that the limits of the primary
segments remain perfectly evident until the antheridium is
nearly full grown.

The central cells in the fresh antheridium are strongly
refringent, and in stained sections show a much more granular
consistence than the outer ones. The nucleus, as in other
cases studied, uses its nucleolus before the formation of the
spermatozoids begins. The latter in their structure and
development correspond with those of Sphagnum, but owing to
their smaller size are not favourable for studying the minute
details of development.

In the peripheral cells are numerous chloroplasts which
lie close to the inner wall of the cell in the ripe antheridium.

I90

MOSSES AND FERNS

CHAP.

As the antheridium ripens, these gradually assume a bright
orange -red colour. The development of the stalk varies in
different cases. Sometimes it consists of a row of several
cells, sometimes the antheridium is almost sessile. The

Fig. 91. — Funaria hygrometrica (Sibth.)- A, Antheridium that has just discharged the ma^ of
sperm cells (B), X300; C, spermatozoids, XZ300; D, paraphysis, X300; £, male "flower" of
Attichum nnduUitum. X6

lowermost segments of the apical cell help to form the upper
part of the stalk, and sometimes the two lowest seem to
take no part in the formation of the sperm cells. There is no
absolute uniformity in the cell divisions of the stalk, which

THE BRYINE^

191

varies in the arrangement of the cells in different individuals in
the same inflorescence.

If ripe antheridia are placed in water, they open within a
few minutes. The peripheral cells become much distended,
especially the terminal ones ; and the chromatophores being
entirely confined to the inner part of the cells, the antheridium
seems to be surrounded by a layer .of perfectly hyaline cells.
The dehiscence takes place at the summit between the terminal
cells, which are simply separated without rupturing their walls.
As soon as the mass of sperm cells is ejected, the opening closes
completely and the empty antheridium looks very much as it
did before, except that it is slightly contracted below. The
whole mass of sperm cells is thrown out without separating the
cells, and in this stage the walls of the sperm cells are still very
evident. It sometimes happens that the mass is thrown out
before the spermatozoids are complete, in which case they never
escape. If, however, the spermatozoids are mature, they show
active motion within the sperm cells while these are still in
connection, and are set free by the gradual dissolution of the
mucilaginous walls. The free spermatozoid is much like that
of Sphagnum^ but the body is somewhat shorter. The cilia
are relatively very long and thick, and as in all Bryophytes but
two in number. A small vesicle can usually be seen attached
to the posterior end.

Growing among the antheridia are found peculiar sterile
hairs, or paraphyses. These in Funaria are very conspicuous,
and consist of a row of cells tapering to the base, and very
much larger at the apex. The terminal cell, or sometimes two
or three of them, are almost globular in form and very much
distended. All the cells of the paraphyses contain large
chloroplasts which in the globular end cells are especially con-
spicuous and often elongated with pointed ends.

The archegonia are formed while the female plant is still
very small, and it is much more difficult to recognise the female
plants than the males. The archegonia are ripe at a time when
the female plant is still but a few millimetres in height. In this
case there is no doubt that the apical cell forms an archegonium
directly, but not necessarily the first one, which arises usually
from one of the last-formed segments. The elongation of the
axis of the female branch is but slight, even in the later stages,
and the plant remains bud-like even after the sporogonium is

192

MOSSES AND FERNS

CHAP.

developed. In regard to the development of the leafy axis, or
gametophore, therefore, Funaria offers a very marked contrast
to Fontinalis or Sphagnum, where the gametophore reaches such
a large size and has practically unlimited growth.

The young archegonia are quite colourless, and the details

Fig. 92.— Longitudinal section through the apex of a male plant of F. hygrontetrica, X 300 ; U leaf;
i , antheridia ; /, paraphyses.

of their structure may be made out without difficulty. The first
division separates a basal cell from a terminal cell, which is the
mother cell of the archegonium. In the latter three walls now
arise, as in the Hepaticae and Andrecea, but in Funaria these do
not all reach to the basal wall, but intersect at some distance above
it, so that they enclose a tetrahedral cell, pointed below instead

THE BRYINE^

193

of truncate. This tetrahedral cell now divides by a transverse
wall into an upper cell, corresponding to the " cover cell " of
the Liverwort archegonium, and an inner one (Fig. 93, A),

which gives rise, as in the Hepaticae, to the egg and ventral
canal cell. From this point, however, the development proceeds
in another way, and follows the method observed in Andrecea.

194

MOSSES AND FERNS

CHAP.

The cover cell, instead of dividing by quadrant walls, has a
regular series of segments cut off from it, and acts as an apical
cell. These segments are cut off parallel both to its lateral
faces and base, and thus form four rows of segments, the three
derived from the lateral forces forming the outer neck cells, and
the row of segments cut off from the base constituting the
axial row of neck canal cells. Each row of lateral segments . is
divided by vertical walls, and forms six rows, which later divide
by transverse walls as well, so that the number of cells in each
row exceeds the original number of segments. This is not the
case with the canal cells, which, so far as could be determined,
do not divide after they are first formed. The wall of the
venter owes its origin entirely to the three peripheral cells
formed by the other primary walls in the archegonium mother
cell. This becomes two-layered before the archegonium is
mature, and is merged gradually into the massive pedicel, which
in the Mosses generally is much more developed than in the
Hepaticae. In the older archegonia the neck cells do not
stand in vertical rows, but are somewhat obliquely placed,
owing to a torsion of the neck during its elongation. From
the central cell the ventral canal cell is cut off, as usual, but is
relatively smaller than is usual among the Hepaticae. The
egg shows a distinct receptive spot, which is not, however, very
large. The rest of the ^gg shows a densely granular appear-
ance, and the moderately large nucleus shows very little colour-
able contents, beyond the large central nucleolus.^ The
terminal cells of the open archegonium diverge widely, giving
the neck of the archegonium a trumpet shape (Fig. 93, F).
Usually some of the cells become detached and thrown off.

The Embryo

The first (basal) wall in the fertilised ovum divides it into
an upper and lower cell, as in Sphagnum and Andreaa^ and
the next divisions correspond closely to those in the latter.
In both cells a wall is formed intersecting the basal wall, but
not at right angles. This is especially the case in the upper
cell, where a second wall strikes the first one nearly at right
angles, and establishes the two-sided apical cell by which the

* It is perhaps questionable whether this mass is really the nucleolus. It may be
composed in part of closely aggregated chromosomes.

VII

THE BRYINEjE

195

embryo grows for a long time. In the lower cell the divisions

^ /.

B. 2.

Fig. 94. — Funaria hygrwntirica (Sibth.). Development of the embryo. A, Optical section of a very
young embryo ; B, C, surface view and optical section of an older one, X 600 ; C, D, longitudinal
sections of the apex of older embryos, x 600 ; rit, endothecium ; am, amphithecium.

are somewhat less regular, but here also it is not uncommon

196

MOSSES AND FERNS

CHAP.

to find a somewhat similar state of affairs, so that the embryo
may be said to have two growing points, although the lower
end shows neither such regular nor so active growth as the
upper one. In the latter the divisions follow each other with
almost mathematical precision. There seems to be no rule as
to how many segments are cut off from the apical cell before
it ceases to function as such, but it is very much larger than
in Andreceay and the embryo soon becomes extremely elongated.
A series of transverse sections of the young sporogonium shows
very beautifully the succession of the first walls in the young
segments. In a section just below the apex (Fig. 95, A), each

Fig. 95. — Five transverse sections of a young embryo of F. hygrometrica. A, Just below the apex,
tlie others successively lower down ; en^ endothecium, X 450.

segment is seen to be first divided by a median wall into two
equal cells. In Funaria usually the next division wall is
periclinal, and at once separates endothecium and amphithecium.
In most other Bryineae that have been examined, however,
and this may also occur in Funaria (see Fig. 95, A), the
second walls formed in the young segments are anticlinal, and
it is not until the third set of walls is formed that the separation
of endothecium and amphithecium is complete. The next
divisions (Fig. 95, C) are in the amphithecium, and separate
it into two layers. In the endothecium now a series of walls
is formed, almost exactly repeating the first divisions in the
original segment (Figs. D, E), and transforming it int6 a group

THE BRYINE^

197

of four central cells and eight peripheral ones. Each of the
latter divides twice by intersecting walls, so that a group of
about sixteen cells (Fig. 96, A) occupies the middle of the
endothecium. The eight peripheral cells divide by radial walls,
after which each of these cells is divided by a periclinal wall
into an outer and an inner cell (Fig. 96, B), and the outer
cells divide rapidly by radial walls and form the archesporium.
The single layer of cells immediately within, and therefore sister
cells of the primary archesporial ones, is the inner spore-sac.
The account of the development of the endothecium here

Fig. 96.- -Three transverse sections of an older sporogonium of F. kygroffutrica^ X 400 ;
or, archesporium; /, intercellular spaces.

given differs slightly from the account of Kienitz-Gerloff.^ It
was found first that there was not the absolute constancy in
the number of cells given by him ; thus in Fig. 96, A there
are only fourteen cells in the inner part of the endothecium,
and although there are sixteen cells in the outer row their
position is not perfectly symmetrical. Again the periclinal
division of the cells of the inner spore -sac takes place later
than he states is the case.

In the eight primary cells of the amphithecium there first
arise periclinal walls that divide each cell into an inner small

1 Kienitz-GerloflF (2).

198

MOSSES AND FERNS

CHAP. VII

cell in contact with the endothecium, and an outer larger one.
This first division separates the wall of the capsule from the
outer spore-sac. The latter next divides by radial and trans-
verse walls, and later by periclinal walls into two layers (Fig.
96). Almost coincident with the latter, the rows of cells
lying immediately outside it show a very characteristic appear-
ance. They cease to divide, and with the rapid growth in
diameter of the capsule become much extended both vertically
and laterally, but are compressed radially. It is between these
cells and the spore-sac that the characteristic air-space found
in the capsule is formed. This is first evident shortly after
the enlargement of the base of the capsule begins. The
development can be very easily followed in longitudinal
sections made at this stage. The formation of the space
begins at the base of the capsule and proceeds toward the top.
The line of cells bordering on the spore-sac is very easily
followed, owing to their being so much larger than the neigh-
bouring ones. As this is followed down, it is found that at
the base of the capsule the cells are separated by large
intercellular spaces, which become less marked toward the
apex. With the rapid enlargement of the capsule these spaces
become very large, and sections made a little later show that
during this process the cells remain in contact at certain
points, and form short filaments that extend across the space
and unite the wall of the capsule with the outer spore -sac.
At the base of the capsule the formation of intercellular spaces
is not confined to the single layer of cells but involves the
whole central mass of tissue, which becomes thus transformed
into a bundle of filaments connecting the columella with the
basal part (apophysis) of the capsule. The innermost of the
two layers of cells between the archesporium and the air-space
finally undergoes a second periclinal division, and in the full-
grown sporogonium the archesporium is bounded on the
outside by three layers of cells.

The differentiation into seta and capsule takes place late
in Funaria^ and the first indication of this is the enlargement
of a zone between the two, forming the apophysis, which at
this stage (Fig. 97) is much greater in diameter than the
upper part of the capsule. Sections through the apophysis
and seta show a less regular arrangement of the cells than the
sporiferous part of the capsule, but the general order of cell-

Fic. 97. — Funaria hygromeirica{S\hth.). A, Longitudinal section of a sporogonium showing the first
differentiation of its parts, X about 96 ; B, the upper part of the same, x6oo ; r marks the limits
of the theca and operculum ; C, basal part of the capsule of the same, x6oo. The intercellular
spaces are beginning to form ; ar, archesporium ; col^ columella.

200

MOSSES AND FERNS

succession is the same, except for the formation of the arche-
sporium. Almost as soon as the capsule is recognisable, the
first indication of the operculum or lid becomes evident.
About half-way between the extreme apex of the sporogonium
and the top of the apophysis, a shallow depression is noticed
extending completely round the capsule and separating the
sharply conical apex from the part below. An examination of
a longitudinal section at this point shows that at the point of
separation the epidermal cells of the opercular portion are

Fig. 98.— Longitudinal section of an older capsule of F. hygrometrica ; r, intercellular spaces ;
i/, archesporium ; r, cells between operculum and theca, X 525.

much narrower than those immediately below. Examining
the tissues farther in, the archesporium is seen to extend only
to a point opposite the base of the operculum, and the same is
true of the row of large cells where the air-space is formed.
If a similar section is made through an older capsule (Fig. 98)
it is evident at once that the enlargement takes place mainly
below the junction of the operculi^m, and there is also a similar
but less pronounced increase in diameter in the operculum
itself; but there is a narrow zone at the junction of the oper-
culum and capsule, where the epidermal cells increase but

THE BRYINEJE

20 1

little in depth, while those above this point become very much
larger and project beyond them. This narrow zone of cells
marks the point where when ripe the operculum becomes
detached. The latter, up to the time the sporogonium is ripe,
is composed of a close tissue without any intercellular spaces.
The epidermal cells, seen from the surface, are seen to be
arranged in spiral rows running from the base to the apex.
Its central part is made up of large thin^alled parenchyma,
continuons with the tissue of the columella. The archesporium,
therefore, is not continuous over the top of the columella, as in
Sphagnum and Andrecea^ but is cylindrical. The archesporium
forms simply a single layer of small cells, and occupies a very
small part of the sporogonium, much less, relatively, than in
any of the forms hitherto described. Before the final division
of the spores it divides more or less completely into two layers.
The cells resulting from this last division are the spore mother
cells, which separate soon after their formation and lie free in the
space between the inner and outer spore-sacs, where each one
divides into four tetrahedral spores.

In the operculum, as the capsule approaches maturity, the
differentiation of annulus and peristome takes place. The
former consists of about four rows of cells (Fig. 98) that occupy
the periphery of the broadest part of the operculum. These
cells are very much compressed vertically, but are deep and
have their walls thicker than their neighbours. Just below
them are about two rows of similar cells, but somewhat less
compressed and with very thin walls. These latter cells mark
where the separation takes place, the annulus forming the rim
of the loosened operculum.

The peristome arises from the fifth layer of cells from the
outside of the operculum. If a median longitudinal section of
a nearly ripe capsule is examined, the row of cells belonging
to this layer (Fig. gg^per) is at once seen to have the outer
walls strongly thickened, and this thickening extends for a
short distance along the transverse walls. The inner walls
of the cells also show a slight increase in thickness, but much
less marked than the outer ones. A similar thickening of the
cell walls occurs also in about three rows of cells which run
from the outside of the capsule to the base of the peristome,
and form the rim of the " theca " or urn.

The epidermis of the whole capsule has its outer walls

202

MOSSES AND FERNS

CHAP.

very much thickened, and upon the apophysis are found
stomata quite similar to those found upon the sporogonium
of Anthoceros or the leaves of vascular plants. Haberlandt^
showed that while the form of the fully -developed stoma
in Funaria differs from that of most vascular plants, this
difference is secondary, and that in its earlier stages no
difference exists. This can be easily verified, and with little
difficulty all the different stages found. The young stoma

Fig. 99. — A, Longitudinal sections of a nearly ripe capsule of F. hygrontetrica^ X a6o ; >rr, peristome ;
r, annulus ; /, thickened cells forming the margin of the theca ; B, the sporogenous cells shortly
before the final divisions ; /, inner ; <?, outer spore-sac, X 525.

(Fig. 10 1) has the division wall extending its whole length,
as is the case in stomata of the ordinary form. As the stoma
grows larger, however, the median wall does not grow as fast
as the lateral walls, and a space is left between its extremities,
so that the two guard cells have their cavities thrown into
communication, and the division wall forms a cellulose plate
extending from the lower to the upper surface of the stoma,
but with its ends quite free. The formation of the pore by
the splitting of the middle lamella of the division wall takes

^ Haberlandt (4), p. 464.

THE BRYINE^

203

place in the ordinary way. Later the walls of the epidermal
cells become very thick and show a distinct striation (Fig.
1 01). By the formation of the stomata the green assimi-
lating tissue of the apophysis and central part of the
capsule are put into direct communication with the external
atmosphere.

The lower part of the seta grows downward and penetrates
the top of the stem of the gametophyte, from which, of course,
it derives a portion of its sustenance. The centre of the seta
is traversed by a well-marked central cylinder, whose inner
cells are small and thin-walled, and are mainly concerned in
conducting water ; immediately outside of this is a circle of

Fig. 100.

xoo. — Longitudinal section of a fully-developed sporogonium of Funaria kygrometricay X about
40 ; X, seta ; a, apophysis ; x/, spores ; col^ columella ; r, annulus ; o^ operculum.

thick-walled brown cells (Leptome of Haberlandt), and the
rest of the seta is made up of nearly similar thick-walled cells
which grow smaller towards the periphery.

At maturity, as the supply of water is cut off from below,
the capsule dries up, and all the delicate parenchyma com-
posing the columella and inner part of the operculum, as well
as that between the spore-sac and the epidermis of the theca,
completely collapses, leaving little except the spores themselves,
and the firm cell walls of the peristome, and the cells connecting
the latter with the wall of the capsule. By the breaking down
of the unthickened lateral and transverse walls of the peristomial
cells, the outer and inner thickened walls are separated and

204

MOSSES AND FERNS

CHAP.

form the two rows of membranaceous teeth that surround the

Fig. ioi. — Funaria hygronutrica (Sibth.)> A, Young; B, older stoma^ from the base of the capsule ;

C, vertical section, X 360.

mouth of the urn (Fig. 102). By the drying up of the thin-
walled cells between the annulus and the margin of the theca
the operculum is loosened and is very easily separated. The

Fig. xo^.— Funaria hygronutrica (Sibth.). A, Part of the peristome ; Oy an outer tooth ; «, one of the
inner teeth, X85 ; B, section of the seta, xa6o ; C, cross-section of upper part of calyptra, X525.

teeth of the peristome are extremely hygroscopic, and probably

VII

THE BRYINE^

205

assist in lifting off the operculum as well as removing the
spores from the urn. When wet they bend inward, extending
into the cavity of the urn. As they dry they straighten out
and lift the spores out. The marked hygroscopic movements
of the seta also are no doubt connected with the dissemination
of the spores.

The calyptra in the Bryineae is very large and is carried
up on the top of the sporogonium in the form of a conspicuous
membranaceous cap. As in other forms it is the venter alone
that shows secondary growth. In Funaria it increases very
much in diameter at the base, where it is widened out like a
bell, and far exceeds in diameter the enclosed embryo. Above
it is narrow and lies close to the embryo. After a time the
embryo grows more rapidly in length than the calyptra, which
then is torn away by a circular rent about its base, and is
raised on top of the elongating sporogonium. The lower
portion remains delicate and nearly colourless, but the upper
part has its cells thick-walled and dark brown in colour (Fig.
102, C). Tipping the whole is the persistent dark brown neck
of the archegonium.

Classification of the Bryinea

The simplest of the Bryineae are the cleistocarpous fornis
or those in which there is no operculum developed, and in
consequence the capsule opens irregularly. If Archidium is
removed from this group the simplest form known is
Ephemerum, Here, from a highly-developed filamentous pro-
tonema, are produced the extremely reduced gametophores.
nJ^ According to Muller,^ who has studied the life-history of this
genus, both male and female branches arise from the same
protonema, and are only distinguishable by the smaller size
of the former. The. axis of the branch is scarcely at all
elongated, and the leaves therefore appear close together.
The sexual organs correspond closely in origin and structure
to the other Bryineae. The development of thfe sporogonium
in its early phases is also the same, and the differences only
appear at a late stage. The separation of endothecium and
amphithecium is apparently exactly the same as in other
Bryineae, and from the former is derived the archesporium,

1 MiiUer (2).

Fic. 103.— A, Longitudinal section of the young sporogomnm of Plcuridium suhtlatum^ x8o; B,
part of the'same, X 600 ; jr/, archesporium ; C, young embryo of Phascum cuspidaium^ optical
section, X 175 ; D, cross-section of an older embryo of the same, x 350 ; */, archesporium ; E, longi-
tudinal section of the central part of the young sporogonium of Ephemerum phascoides^ x 35c ;
</, archesporium. C, D, after Klenitz-Gerloff ; E, after Milller.

CHAP. VII

THE BRYINE^

207

which like that of Funaria has the form of a hollow cylinder
through which the columella passes. Between the outer
spore-sac and the wall of the sporogonium an intercellular
space is also formed, but the separation of the cells is
complete, and there are no filaments connecting the spore-sac
and the sporogonium wall as in Funaria, The cells of the
archesporium are few in number and correspondingly large
(Fig. 103, E), and before the division into the spores takes
place all the central tissue of the columella is absorbed, and
the spore mother cells occupy the whole central space. Here
the division of the spores is completed, and at maturity the
whole of the capsule is filled with
the large spores, and no trace of the
columella remains.

The highest members of the
Cleistocarpae, such as Phascum and
Pleuridium (Fig. 104), approach
very closely in structure the stego-
carpous Bryineae. In these . the
gametophore is much better devel-
oped than in Ephetnerum^ and the
protonema not so conspicuous. The
leaves also frequently have a well-
developed midrib which is wanting
in the leaves of Ephemerunt.

Kienitz-Gerloff ^ has carefully
studied the embryogeny of Phascum
cuspidatunty and except in a few
minor details it corresponds very closely to that of Funariay ex-
cept, of course, as regards the operculum and peristome, which
are absent In Phascum^ however, the archesporium is differen-
tiated earlier than in Funaria, In each of the four primary cells
of the endothecium, as seen in transverse section, a periclinal
wall arises which at once separates the archesporium from the
columella (Fig. 103, D). The outer spore-sac has but two
layers of cells, and the capsule waH three, and between them
the large lacuna is formed as in Futictria ; but in Phascum as
in Ephemerum, the separation of the celh is complete. In the
seta a slightly-developed central cylinder of conducting tissue
is developed, derived, as in Funaria, froi^ the endothecium,

1 Kienitz-Gerloff (2).

Fig. \o^,— Pleuridium subulaium, X ao.

2o8 MOSSES AND FERNS chap.

but in Phascum it is much less conspicuous. Pleuridium (Fig.
103, A) in its later stages corresponds exactly to Phascum^
except that the capsule is more slender. In both of these
genera the seta remains short, but is perfectly evident.
Whether the absence of a distinct operculum in the cleisto-
carpous Mosses is a primitive condition, or whether they are
reduced forms, it is impossible to determine positively from a
study of their embryogeny.

BryinecB Stegocarpce

Very much the larger number of Mosses belong to this
group, which is primarily distinguished from the foregoing by
the presence of an operculum. Of course among the 7000 or
more species belonging here there are many differences in
structure ; but these are mainly of minor importance morpho-
logically, and only the more important differences can be con-
sidered here.

As we have already seen, there is great uniformity in the
growth of the stem, which, with the single exception oi Fissidens^
has always a three-sided pyramidal apical cell. In Fissidens
this is replaced by a two-sided one, but even here it has been
found ^ that the underground stems have a three-sided initial
cell, which is gradually replaced by the two-sided one after the
apex of the shoot appears above ground. In Fissidens the
leaves are arranged in two rows corresponding to the two sets
of segments, and are sharply folded, so that the margins of the
leaf are covered over by those of the next older ones, leaving
only the apex free. A similar arrangement is found in the
genus Bryoziphion {Eustichid)^ but here there is a three-sided
apical cell, and the two-ranked arrangement of the leaves is
secondary. The curious genus Schistostega shows also a t\v'0-
ranked arrangement of the leaves of the sterile branches, but
here they are placed vertically and the bases connivent, so that
the effect of the whole is thajfe-fjf a pinnatifid leaf. The fertile
branches, however, have the/leaves spirally arranged, and in the
sterile ones the three-ssdjfed apical cell is found. The leaves,
with few exceptions, j^^ Leucobryum^ Fontinalis, have a well-
marked midrib, and Ai^^ lamina is single-layered. Leucobryum
(Fig. 107, A) has !«/ g destitute of a midrib, and made up of

X Goebel (8), p. 37i.

THE BRYINE^

209

two or three layers of cells, large hyaline ones, somewhat as in
Sphagnum^ and small green cells. The hyaline cells, as in
Sphagnum^ have round holes in the walls, but no thickenings*
The midrib may be narrow, as in Funaria^ or it may occupy
nearly the whole breadth of the leaf, as in the Polytrichace^e,
where, owing to the almost complete suppression of the lamina,
secondary vertical plates of green cells are formed (Fig. 107, B).

The one-third divergence of the leaves found in Fontinalis ^ is
replaced in most other genera by a larger divergence." Thus
in Funaria hygrotnetrica it is ^ ; in Polytrichum commune ^^ ;
in P./ormosum J^.

As the archegonia are borne upon lateral branches, or upon
the main axis, the stegocarpous Bryineae are frequently divided
into two main divisions, the Pleurocarpae and the Acrocarp^e,
which are in turn divided into a number of subdivisions or
families. How far the division into acrocarpous and pleuro-
carpous forms is a natural one may be doubted, as probably the
latter is secondary, and it is quite conceivable that different
families of pleurocarpous forms may have originated inde-
pendently from acrocarpous ones.

The simplest of the stegocarpous Mosses, while having the
operculum well marked, have no peristome. Thus the genus
Gymnostomum has no peristome at all, and in an allied genus,
Hymenostomunty it is represented by a thin membrane covering
the top of the columella. In nearly related genera, however,
e.g. Weisiay a genuine peristome is present.

The Tetraphideae, represented by the genus Teiraphis (Fig.
105), are interesting as showing the possible origin of the
peristome, as well as some other interesting points of structure-
Tetraphis pellucida is- a small Moss, which at the apex of its
vegetative branches bears peculiar receptacles containing muUi-
cellular gemmae of a very characteristic fprm. The leaves that
form the receptacle are smaller iJ^n ^he stem leaves, and
closely set so as to forn> a sort of cup, h^, which the gemmae are
produced in large numbers. These ari^e as slender multi-
cellular hairs, the end cell of which enlarg'^s and forms a disc,
at first one-layered, but later, by walls parallel to the brosid
surfaces, becoming thicker in the middle, and denticular in form.
The arrangement of the cells in the young genini£e looks as if

^ Thb seems to be strictly the case only in the smaller branchc* ? i^ the larger iLxea
the leaves are not exactly in three rows. ^ Goebel s^)-

MOSSES AND FERNS

CHAP.

the growth of the bud was due to a, two-sided apical cell (Fig.
105, C), but this point was not positively determined. These
gemmae give rise to a protonema of a peculiar form, from which
in the usual way the leafy stems develop. The protonema!
filaments grow into flat thalloid expansions that recall those of
Sphagnum and Andrecea,

The sporogonium of Tetraphis has a peristome of peculiar
structure, and not strictly comparable to that of any of the

Fig. 10$.— Tetraphis peliucida (Hedw.). A, Plant with gemmae, x6; B, upper part of the
X50; C, young gemma, x6oo; D, a fiiliy-dcvelopcd gemma, X300.

other Mosses. After the "oosfculum falls off the tissue lying
beneath splits into four og^ted teeth, which, however, are not,
as in FunariUy compqg^ simply of the cell walls, but are
masses of tissue. /

All of the oth^Ugher Bryineae, with the exception of the
Polytrichaceae, ha^^ ^^e peristome of essentially the same struc-
ture as that des^j-j^^d for Funaria, Sometimes the teeth do
not separate bu^ remain as a continuous membrane, ix, the
inner perfstomxf ^^ ^uxbaumia, or a perforated membrane, as in
Fontinalis {Yx^.^^ i 06, B).

VII

THE BRYINE^

The base of the capsule, or apophysis, which Haberlandt ^

Fig. xo6.— a, SplachnumampuUaceumiX^X longitudinal section of the sporogonium(aAer Haberlandt) ;
a, apophysis ; c, capsule ; B, peristome cli Fontinalis antipyretica (L.) ; C, peristome <A Atrichum
undulatum (after Schiraper) ; D, sporogonium of Polytrichum commune (L.) : i, with the
calyptra ; 3, with the calyptra removed ; E, Buxbaumia^ X4.

has shown to be the principal assimilative part of the sporo-

^ Haberlandt (4).

212 MOSSES AND FERNS chap.

gonium, and which alone is provided with stomata, sometimes
becomes very large, and in the genys Splachnum^ especially
forms a largely -developed expanded body, which must be
looked upon as a specially -developed assimilating apparatus
(Fig. 1 06, A).

Undoubtedly the Polytrichaceae represent the highest stage
of development among the Musci. This is true both in r^rard
to the gametophore and the sporogonium. The former reaches
in some species, i,e, P, commune^ a length of 20 centimetres
and sometimes more. The stem is usually angular and the
closely-set leaves thick and rigid. The numerous rhizoids are
often closely twisted together and form cable-like strands. The
structure of the leaves is very characteristic, and differs very
much from that of the simpler type found in Funaria. In
Polytrichum (Fig. 107, B) the midrib is very broad, and only
at the extreme margins of the leaf is the lamina one-layered.
Seen in cross -section ^ the leaf appears somewhat crescent-
shaped. The cells of the margin of the section, and also a line
of cells running through the central part, are comparatively thin-
walled, and the latter are empty water-conducting cells similar
to the tracheae in the vascular bundles of the higher plants.
Next to these cells on the lower side of the leaf are a number
of similar but somewhat smaller cells containing starch, and the
rest of the section is made up principally of very thick-walled
sclerenchyma. The outer cells contain more or less chloro-
phyll, but the principal assimilative tissue consists of a series
of vertical cell plates or laminae parallel to the long axis of the
leaf, and seen in cross-section appear as short vertical rows of
four or five cells. These cells contain numerous chloroplasts,
and the laminae cover the whole upper surface of the leaf
except the extreme margin and the sheathing part of the base,
where they are wanting.

The structure of the stem of P, commune is thus described
by Goebel.® " A transverse section of the stem shows the
following structure. In the centre is a cylinder of broad thick-
walled cells, with here and there those whose walls have remained
thin. The thickened walls show a yellowish colour. Surround-
ing this cylinder is a ring of several layers of thin-walled narrow
cells, which is bounded on the outside by from one to three
layers of cells with thin, mostly very dark brown walls. These

* Vaity (3). » Strasburger (10). ' Goebel (8), p. 369.

VII

THE BRYINE^

213

latter, as well as the
are characterised by the
starch contained in them,
as are the narrow cells of
the leaf- traces. Other-
wise starch is often com-
pletely absent from the
stem of Polytrichutn and
is replaced by oil. The
latter is abundant, and
probably albuminoids as
well, in the thin -walled
tissue surrounding the
central cylinder. In the
latter oil is not so abund-
ant, as its cells for the
most part contain only
air."

The leaf - traces, or
continuation of the central
tissue of the midribs of
the leaves, bend down
into the stem, and fin-
ally unite with the axial
cylinder of the latter, in
a manner quite analogous
to that found in the stems
of many vascular plants.

Bastit,^ who more re-
cently has made a com-
parative study of the
subterranean and aerial
stems of P, juniperinufHy
divides the outer tissue
of the latter into epi-
dermis, hypoderma, and
cortex. In the subter-
ranean stems he finds the
construction quite differ-
ent from that of the leafy

Fig. 107. — A, Transverse section of the leaf of Leuc<h
brjrum ; B, similar section of the leaf of Polytrichum
commune; cl^ chlorophyll'bearing cells (after Goebel).

Bastit (I), p. 295.

214 MOSSES AND FERNS chap.

branches. The section of the former is triangular, and its epi-
dermis provided with hairs which are absent from the epidemnis
of the aerial parts. Rudimentary scales, arranged in three rows,
are present, and corresponding to these are strands of tissue
that represent the leaf-traces of the aerial stems. The central
cylinder is much larger relatively than in the leafy branches,
and its cross-section is not continuous, but is interrupted by-
three " pericyclic sectors," composed of cells whose walls are
but little thickened. The point of each sector is at the peri-
phery of the medulla, or central cylinder, and the broad end
toward the centre. As might be expected, intermediate con-
ditions are found where the rhizome begins to grow upward to
form a leafy branch.

The male inflorescence of the Polytrichaceae is especially
conspicuous, as the leaves imiyiediately surrounding the anther-
idia are different both in form and colour from those of the
stem. They are broad and membranaceous, and more or less
distinctly reddish in colour. A well-known peculiarity of these
forms is the fact that the growth of the stem is not stopped
by the formation of antheridia, but after the latter have all
been formed the axis resumes its growth and assumes the
character of an ordinary leafy branch. This, of course, indicates
that, unlike most of the Mosses, the apical cell does not become
transformed into an antheridium, and the researches of Hof-
meister,^ Leitgeb,^ and Goebel^ have shown that this is the
case. The antheridia form groups at the base of each leaf of
the inflorescence, and Leitgeb thinks it probable that each
group represents a branch, t.e. the inflorescence is a compound
structure, and not directly comparable to the simple male
inflorescence of Funaria, ,The sporogonium in Polytrichum
has a large intercellular space between the inner spore-sac and
columella as well as the one outside the outer spore-sac In
both cases the space is traversed by the conferva -like green
filaments found in the other stegocarpous Mosses. The apo-
physis is well developed, especially in Polytrichuniy and the
calyptra very large and covered with a dense growth of hairs
(Fig. 1 06, D).

The* structure of the peristome in the Polytrichacese is
entirely different from that of the other Mosses. It is com-
posed of bundles of thickened fibrous cells arranged in crescent

^ Hofineister (2). a Leitgeb (9). ' Goebel (7).

VII

THE BRYINE^

215

form, the ends of the crescent pointing up, and united with the
adjacent end of the bundle next it. The tops of the teeth thus
formed are connected by a layer of cells stretching across the
opening like the head of a drum. This membrane is known
technically as the " Epiphragm " (Fig. 1 06, C).

The Buxbaumiacea

The last group of Mosses to be considered is the very
peculiar one of the Buxbaumiaceae. In these Mosses the
gametophyte is extraordinarily reduced, although the sporo-
gonium is large and well developed. So simple is the sexual
plant, that Goebel ^ has concluded that these ought to be taken
away from the rest of the Mosses, and removed to a distinct
order. According to GoebeFs 'account, the antheridia, which
are long stalked,^ are borne directly upon the protonema, and
subtended by a single colourless bract. The female branches
are also very rudimentary, but less so than the male. On the
strength of the extreme simplicity of these, Goebel thinks
that Buxbaumia is a primitive form allied to some alga-like
progenitor of the Mosses. There are, however, two very strong
objections to this. First the sporogonium, which is extremely
large, and complicated in structure, and essentially like that of
the other stegocarpous Mosses ; secondly, Buxbaumia has been
shown by Haberlandt ^ to be distinctly suprophytic in its habits,
and the extreme reduction of the assimilative tissue of the
gametophyte is quite readily explicable from this cause.

Fossil Muscinea

The remains of Muscineae in a fossil condition are exceed-
ingly scanty ; so much so indeed as to practically throw no light
upon the question of their origin and affinities, as nearly all of
the forms discovered belong to the later formations, and are
either indentical with living species or closely allied forms.
No doubt the great delicacy of the tissues of most of them,
especially the Hepaticae, accounts in great measure for their
absence from the earlier geological formations.

» Goebel (16).

'-» Haberlandt (4), p. 480.

2i6 MOSSES AND FERNS chap.

The Affinities of the Musci

It is perfectly evident that the Mosses as a whole form a
very clearly defined class, and that their relationship with other
forms is at best a somewhat remote one. Sphagnum^ however,
certainly shows significant peculiarities that point to a
connection between this genus, at least, and the Hepaticae. It
will be remembered that the protonema of Sphagnum is a large
flat thallus, and not filamentous, as in most Bryineae. It is
noteworthy, however, that from the margin of this flat thallus
later filamentous branches grow out which are apparently
identical in structure with the ordinary protonemal filaments of
the Bryineae. In Andrecea similar flat thalloid protonemata
occur, but not so largely developed as in Sphagnum^ and
finally in Tetraphis a similar condition of affairs is met with.
As this occurs only among the lower members of the Moss
series, the question naturally arises, does this have any
phylogenetic meaning ? While it is impossible to answer this
question positively, it at any rate seems probable that it has a
significance, and means that the protonema has been derived
from a thalloid form related to some thallose Liverwort, and
that by the suppression of the thalloid portion, as the leafy
gametophore became more and more prominent, the filament-
ous branches, which at first were mere appendages of the thallus,
finally came to be all that was left of it. The view of Goebel
and others that the filamentous form of the protonema is the
primitive one, and indicates an origin from alga-like forms,
might be maintained if the question were concerned simply with
the protonema ; but when the structure of the sexual oi^ans,
especially the archegonium, is considered, and the development
of the sporophyte, the difficulty of homologising these with the
corresponding parts in any known Alga is apparent, while on
the other hand the resemblance between them and those of
the Hepaticae is obvious.

As to which group of the Hepaticae comes the nearest to
the Mosses, the answer is not doubtful. The remarkable
similarity in the development and structure of the sporogonium
of Sphagnum and the Anthoceroteae, leaves no room for doubt
that as far as Sphagnum is concerned, the latter come nearest
among existing forms to the ancestors of Sphagnum, Of

THE BR VINE ^

217

course this does not assume a direct connection between
Sphagnum and any known form among the Anthoceroteae.
There are too many essential differences between the twos to
allow any such assumption : but that the two groups have
come from a common stock seems reasonably certain, and the
structure of the capsule in Sphagnum points to some form
which like Anthoceros had a highly -developed assimilative
system. This is indicated by the presence of stomata, which,
although functionless, probably were once perfect, and make it
likely that with the great increase in the development of the
gametophyte the sporophyte has lost to some extent its
assimilative functions, which have been assumed by the
gametophyte.

AndreaUy both in regard to the gametophyte and the sporo-
phyte, is in many ways intermediate between Sphagnum and the
other Mosses. The resemblance in the dehiscence of the
sporogonium to that of the Jungermanniaceae is probably
accidental. It may perhaps be equally well compared to the
splitting of the upper part of the capsule into four parts, in
Tetraphisy although in the latter it is the inner tissue and not
the epidermis which is thus divided.

If this latter suggestion proves to be true, then there would
be a direct connection of Andreaa with the stegocarpous
Bryineae, and not through the cleistocarpous forms. These
latter would then all have to be considered as degraded forms
derived from a stegocarpous type, unless, with Leitgeb, we
consider them as a distinct line of development leading up to
the higher Bryineae, entirely independent of the Sphagnaceae,
and with Archidium and Ephemerum as the simplest forms.
His comparison of these forms with Notothylas^ however, cannot
be maintained with our present knowledge of that genus, and
more evidence is needed before his view can be accepted ; but
the possibility of some such explanation of the cleistocarpous
Bryineae must be borne in mind in trying to assign them their
place in the system.

The objections to considering Buxbaumia a primitive form
have been already given, and it is not necessary to repeat
them.

CHAPTER VIII

THE PTERIDOPHYTA OPHIOGLOSSACEiE

In tracing the evolution of the Bryophytes from the lowest
to the highest types the gradual increase in the importance of
the second generation, the sporophyte, is very manifest This
may or may not be accompanied by a corresponding develop-
ment of the gametophyte. In the line of development
represented by the higher Mosses, in a general way the two
have been parallel, and the most highly differentiated
gametophyte bears the most complicated sporophyte, as may
be seen in Polytrichunt, for example ; but in the Hepaticae this
is not the case, and much the most highly organised sporophyte
here, that of AnthoceroSy is produced by a very simple game-
tophyte.

In this evolution of the sporophyte, it approaches a condition
where it is self-supporting, but in no case does it become
absolutely so. A special assimilative tissue, it is true, is
developed, and in some of the true Mosses, such as Splachnum^
this goes so far that a special organ, the apophysis, is formed ;
but, as we have seen, the sporogonium is dependent for its
supply of water and nitrogenous food upon the gametophyte,
with which it remains intimately associated, and upon which it
lives as a parasite.

In the Pteridophytes the case is different; here by the
development of a special organ, the root, the young sporophyte
is brought into direct communication with the source of supply
of water, and the food materials dissolved in it. In the few
cases where true roots are absent their place is taken by other
structures that perform their functions. The assimilative activity
is restricted to special organs, the leaves, except in a few cases

CH. VIII THE PTERIDOPHYTA—OPHIOGLOSSACEjE

219

where these become much reduced, as in Psilotum or Equisetum.
A main axis is present upon which the leaves are borne as
appendages, and which continues to form new leaves and roots
as long as the sporophyte lives.

The differentiation of these special organs begins while
the sporophyte is still very young. The earliest divisions in the
embryo correspond closely to those in the embryo of a Bryo-
phyte, but instead of forming simply a capsule, as in all the
Bryophytes, there is established more than one growing point,
each one forming a distinct organ. In the Ferns there are
four of these primary growing points, giving rise respectively
to the stem, leaf, root, and foot. The latter is a temporary
structure, by which the young sporophyte absorbs food from the
gametophyte, but as soon as it becomes independent this
gradually withers away, and soon all trace of it is lost.

The originally homogeneous tissues of the embryo become
differentiated into the extremely complicated and varied tissues
characterising the mature sporophyte. The most characteristic
of these are the vascular system of tissues. This is hinted at
in the central strand of tissue in the seta of many Mosses, and
the columella of the Anthoceroteae ; but in no Bryophyte does
it reach the perfect development found in the Ferns and their
relations, which are often called on this account the vascular
cryptogams.

The gradual reduction in the vegetative parts of the
gametophyte, from the large long-lived prothallium of the
Marattiaceae to the excessively reduced one found in the
heterosporous Pteridophytes, has already been referred to in
the introductory chapter.

The structure of the sexual organs of the Pteridophytes
appears at first sight radically different from that of the
Bryophytes, but a careful comparison of the lower forms of the
former with some of the Hepaticae, especially the Anthoceroteae,
shows that the difference is not so great as it at first sight
appears. A further discussion of this point must be left, how-
ever, until we have considered more in detail the structure of
these parts in the different groups of the Pteridophytes, where
they are remarkably uniform. In all of them the archegonium
has a neck composed of but four rows of peripheral cells, instead
of five or six, as in the Bryophytes, and the antheridium, except
in the leptosporangiate Ferns, is more or less completely sunk

220 MOSSES AND FERNS chap.

in the tissue of the prothallium. The spermatozoids are either
biciliate, as in Mosses, or multiciliate, a condition which, so far
as is known, does not exist among the Bryophytes.

The formation of spores is very much more subordinated
to the vegetative life of the sporophyte than is the case among
the most highly organised of the Bryophytes. Indeed it may be
many years before any signs of spore formation can be seen.
The spores are always bom in special organs, sporangia, which
are for the most part outgrowths of the leaves, but may in a
few cases develop from the stem. In the simplest cases the
spores arise from a group of hypodermal cells, generally trace-
able to a single primary cell. The cell outside of these divides
to form a several-layered wall, but the limits of the sporangium
are not definite, and it may scarcely project at all above the
general surface of the leaf. From this condition found in
Ophioglossum^ there is a complete series of forms leading to the
so-called leptosporangiate type, where the whole sporangium is
directly traceable to a single epidermal cell, and where a very
regular series of divisions takes place before the archesporium
is finally formed.

With very few exceptions all of the existing Pteridophytes
fall naturally into three series or classes of very unequal size.
The first of these, the Ferns or Filicineae, is the predominant
one at present, and includes at least nine-tenths of all living
Pteridophytes. The Equisetineae are the most poorly repre-
sented of the modern groups, and include but a single genus
with about twenty-five species. The third class, the Lyco-
podineae, is much richer both in genera and species than the
Equisetineae, but much inferior in both to the Filicineae. The
disproportion between these groups was much less marked in
the earlier periods in the world's history, as is attested by the
very numerous and perfect remains of Pteridophytes occurring
especially in the coal-measures. At that time both the
Equisetineae and Lycopodineae were much better developed
both in regard to size and numbers than they are at present.

Class I. Filidnea

The Filicineae, as already stated, include by far the greater
number of existing Pteridophytes, and are much more ex-
tended in range and abundant in numbers than either of the

VIII

THE PTERIDOPHYTA—OPHIOGLOSSACEjE

221

Other classes. A marked characteristic of all Ferns is the
large size of the leaves, which are also extremely complicated
in form in many of them. In a few of these the leaves are
simple, t.e, Ophtoglossum^ Vittariay Pilulariuy but more commonly
they are pinnately compound and sometimes of enormous size.
The stem varies a good deal in form and may be very short
and completely subterranean, as in species of Ophioglossum and
Botrychium^ or it may be a creeping rhizome, or in some of the
large tropical Ferns it is upright, and grows to a height of 8
to lo metres, or even more.

While some forms of the Ferns are found adapted to almost
all situations, most of them are moisture -loving plants, and
reach their greatest development in the damp forests of the
tropics. A few, eg, CeratopteriSy Azolla^ are gtouine aquatics,
and still others, eg, species of Gymnogrammey live where they
become absolutely dried up for several months each year.
These latter will quickly revive, however, as soon as placed in
water, and begin to grow at once. In the tropical and semi-
tropical regions many Ferns are epiphytes, and form a most
Striking feature of the forest vegetation. With few exceptions
the sporophyte is long-lived, but a few species are annual, eg,
Pilularia Atnericanay Marsilia vestitay and depend entirely
upon the spores for carrying the plant through from one season
to another. The sporophyte may give rise to others by simply
branching in the ordinary way, or special buds may be developed
either from the stem or upon the leaves {Cystopteris bulbiferd).

Besides the normal production of the gametophyte from
the spore, it may arise in various ways directly from the
sporophyte (apospory) ; and conversely the latter may develop
as a bud from the gametophyte without the intervention of the
sexual organs (apogamy).

The Filicineae include both eusporangiate and leptospor-
angiate forms, — indeed the latter occur only here. The former
comprise the homosporous orders, Ophioglossaceae and Maratti-
aceae, and the heterosporous order Isoetaceae, whose systematic
position, however, it must be said is still doubtful. The
Leptosporangiatae include the single great homosporous order
Filices, and the two heterosporous families, closely related to
it, the Salviniaceae and the Marsiliaceae. These are usually
classed together as a distinct order, the Hydropterides or
Rhizocarpeae.

222 MOSSES AND FERNS chap.

The Homosporous Eusporangiatce

The two orders, Ophioglossaceae and Marattiaceae, show
many evidences of being very ancient forms, and in several
respects seem to approach more nearly to the Hepaticae than any
other Pteridophytes. While they are different from each other
in many respects, still there is sufficient evidence to indicate
that they belong to a common stock to warrant placing them
near each other in the system.

Tfie Ophioglossacece

The gametophyte of the Ophioglossaceae is still very in-
completely known, and only in a few forms. Mettenius ^
described the older stages of Ophioglossum pedunctdosum^ and
Hofmeister^ similar prothallia of Botrychium lunaria, but they
were unable, as later observers have been, to procure the earlier
conditions. In both cases the prothallia were subterranean
and entirely destitute of chlorophyll. In Ophioglossum^ how-
ever, when it reached the surface of the ground, the part exposed
to the light became somewhat flattened and green.

The earliest stages that Mettenius found consisted of a
nearly globular tubercle, from which a single conical protuber-
ance grew upward, having a branch that in extreme cases
reached a length of as much as two inches (Fig. io8). This
branch grows by a single apical cell, and may occasionally
branch dichotomously, and always grows towards the light.
On reaching the surface of the ground the growth is checked
and a flattened expansion is produced whose cells contain
chlorophyll. The sexual organs are borne almost exclusively
upon the subterranean parts of the branch, and in great
numbers. On the weaker prothallia antheridia prevail, on the
stronger ones archegonia. The structure and development of
these correspond closely with those of the other eusporangiate
Pteridophytes. The antheridia are completely sunk in the
tissue of the prothallium, and the outer wall is composed of
two layers of cells (Fig. io8, C). The archegonia have a short
neck, which projects but little above the surface. The number
of canal cells does not seem to have been determined (Fig.
1 08, D).

* Mettenius (3), p. 119. ^ Hofmeister (i), p. 307.

VIII

THE PTERIDOPHYTA'-OPHIOGLOSSACE^

223

The prothallium of Botrychium lunaria ^ is much smaller and
does not grow to the surface of the ground. It is oval in form,
and consists of a mass of firm tissue, brownish towards the
outside and colourless within, where the cells are also larger.
Scattered root-hairs grow from the superficial cells, and the
prothallia are monoecious. The antheridia, which correspond

Fig. 108. — Ophiogiostum peduMcuiosum (Desv.X A, B, Prothallia, xa; T, the primar>' tubercle;
C, antheridium, X 300 ; D archegonium ; E, a young embryo (after Mettenius).

closely to those of Ophioglossum, are produced principally upon
the upper surface, the archegonia below. The latter correspond
in structure to those of Ophioglossum^ but to judge from
Hofmeister's figure the neck is somewhat longer and projects

* Hofmeister, Lc,

224

MOSSES AND FERNS

more above the surface. The spermatozoids are described as
similar to those of the Polypodiaceae, but half as large again.

The writer has succeeded in securing the earliest phases of
germination in two other species, viz. Ophioglossum {Qphioderma)
pendulum and Botrychium Virginianum^ as well as the older
prothallia of the latter. The germination in both cases is
extremely slow, especially in the former, where a year and a
half after the spores were sown the largest prothallia had but
three cells. Probably under natural con-
ditions the growth is rfiore rapid. The
spores of both forms show much the same
structure. The tetrahedral spores contain
granular matter, with numerous oil -drops,
and a central large and distinct nucleus.
The exospore is colourless, and upon the
outside presents a pitted appearance in
Ophioglossum^ and irregular small tubercles
in Botrychium, The perinium or epispore
is not clearly distinguishable from the
exospore. In both cases chlorophyll is
absent in the ripe spore. The first sign of
germination is the absorption of water and
splitting of the exospore along the three
radiating lines on the ventral surface of the
spore. The spore enlarges considerably
before any divisions occur, but remains
globular in form, and no chlorophyll can
be detected. In this condition, which was
observed within two weeks after the spores
were sown in Ophioglossum^ it may remain
for several months unchanged. The first division wall is usually
at right angles to the axis of the spore, and divides it into two
nearly equal cells, of which the lower has more of the granular
contents than the upper one. The endospore is noticeably
thickened where it protrudes through the ruptured exospore.
The next wall, in all cases observed, is at right angles to the
first, and always in the lower cell, which it divides into equal
parts (Figs. 109, no). In Botrychium at this stage a few
large chloroplasts were seen in both upper and lower cells, but
Ophioglossum showed no positive evidence of chlorophyll,
although it seemed sometimes as if a faint trace of chlorophyll

Fig. 109. — Germinating spore
of Ophiofclostum {pphio'
dermdi pendulum (L.).
A, Surface view ; B,
optical section, x6oo.

VIII

THE PTERIDOPHYTA—OPHIOGLOSSACEJS

225

could be detected. As growth proceeds, the oil partially
disappears, and the cells become much more transparent than
at first. Up to the present writing no further observations have
been made, but it is hoped later that some additional informa-
tion may be obtained on this important point.

In July 1893, at Grosse He, Michigan, the writer was
fortunate enough to find a number of old prothallia of B^trych-
turn Virginianum, They were all connected with the young
sporophyte, and were too old for studying at all completely the

Fic. xio.—BotrycAium t^irginianufn {Sw.). A, B, Germinating spore, x6oo; C prothallium (/r),
with young sporophyte attached, X a ; D, longitudinal section of the prothallium, showing the
foot of the embryo (/>, X 4 ; £, first (f) leaf of a young sporophyte, X 2.

development of the sexual organs and embryo. They resembled
closely those of B. lunaria^ but were very much larger. They
grew at a distance of several centimetres beneath the surface of
the ground, in the neighbourhood of a number of large speci-
mens of the mature plant. The prothallium at this stage, like
that of B, lunaria, is completely destitute of chlorophyll, and
has the form of a slightly flattened tuber, which in the larger
ones showed fold -like ridges upon the upper surface. The
outer cells were brownish, and short root-hairs grew in large

226 MOSSES AND FERNS chap.

numbers from these. The inner tissue was colourless and
large-celled, and in the cells of the lower part of this tissue
were observed in all cases great numbers of irregular colourless
filaments that had all the appearance of an endophytic fungus.
Whether this is of the nature of a mycorrhiza remains to be
seen, but it is by no means impossible that such should be the
case.^ This lower tissue forms a distinct zone, which in section
appears much more opaque than thej upper zone, from whose
outer cells the sexual organs arise.

The sexual organs were found as a rule only upon the
upper side, in which respect it differs from B. lunaria^ where
the archegonia usually are formed on the lower side. The
material was too old to make it possible to tell whether the
growth of the prothallium was from a single apical cell or
not. All of the archegonia found were old, and it was im-
possible to follow their development, and the details of the
structure of the ripe archegonium could not be made out.
A striking point of difference between it and the other forms
hitherto investigated is the long neck, which projects quite
as much above the prothallium as that of the leptosporan-
giate Ferns (Fig. iii, C). In general appearance it closely
resembles that of Osmunda^ being straight and not curved
backward, as in most Ferns. The antheridia may either
occur singly, in which case they are sunk in the thallus, or
sometimes groups of them occur together upon short branches
projecting from the upper surface. In the latter condition the
individual antheridia often project somewhat. So far as could
be judged from a study of a very small number of young
stages, the development corresponds exactly to that in Equiseium
or Marattia, The antheridium mother cell probably, as in
these, divides first by a wall parallel to its outer surface into
two cells, and the inner one divides next by alternate trans-
verse and vertical walls into the mass of sperm cells. In some
cases the outer cell divides both by vertical and transverse
walls, so that the outer wall of the ripe antheridium is two-
layered, as in B, lunaria ; but quite as often it remains but one
cell thick (Fig. 1 1 1, B), in which respect it resembles Equiseium
or Marattia, The spermatozoids were not observed.

In only one case was a young embryo found, and this, so
far as could be determined, also resembled in the arrangement
of its cells the similar condition in Marattia^ but the prepara-

THE PTERIDOPHYTA—OPHIOGLOSSACE^

227

tion was not a satisfactory one, and the results not conclusive.
Although the young plants were so far advanced (Fig. 1 10) it
was a significant fact that the prothallium still remained alive.
A section through the base of the young sporophyte showed
the foot, which is extraordinarily large here, and a microscopic
examination showed that the peripheral cells of the foot were
full of protoplasm, and their nuclei extremely distinct, and the
cells were evidently still actively engaged in absorbing food

Fig. III. — Botrychium Viginianum (Sw.). A, Young; B, older antheridium, longitudinal sections.
A, X 600 ; B, X 300 ; C, section of old archegonium, X 300.

from the prothallium for the support of the sporophyte. The
single leaf in these young plants was not probably the coty-
ledon, which had apparently disappeared, and is probably of
simpler structure.

Hofmeister found that in B. lunaria the first two roots
were formed before the first green leaf, and that the first three
leaves are scale-like. The fourth leaf is the first to appear
above the ground, which it only does the second year, or
possibly later. The position of the archegonium in this species

228 MOSSES AND FERNS chap, viii

upon the lower surface, necessitates a bending upward of the
growing point of the young sporophyte, which is not the case
in B, Virginianum^ where the archegonium is above, and the
sporophyte grows up vertically from the beginning.

Mettenius' account of the development of the embryo in
O. pedunculosunt is somewhat more complete. The earliest
stage seen by him was already multicellular, and the young
embryo had the form of an oval cell mass in which the primary'
divisions were not recognisable (Fig. io8, E). The upper part,
ix, that next the archegonium neck, grows up at once into the
cotyledon, while the opposite part gives rise to the first root.
These grow respectively upward and downward, and break
through the overlying prothallial cells. Later, at a point
between the two, the stem apex is developed. The first leaf
here becomes green, and develops a lamina similar to that of
the later-formed ones. Usually but one embryo is developed
from the prothallium, but occasionally two are formed, especi-
ally where the prothallium forks.

Ophioglossum {Ophiodermd) pendulum^ an epiphyte common
in the Eastern tropics, may be taken as a type of the simplest
of the Ophioglossaceae. Its short creeping stem grows upon
the trunks of trees, especially tree-ferns, from which the long
flaccid leaves hang down. The lamina of the leaf merges
insensibly into the stout petiole whose fleshy base forms a
sheath about the next younger leaf Corresponding to each
leaf is a thick unbranched root, which penetrates into the
crevices of the bark and holds the plant secure. These roots
are smooth, and show no trace of rhizoids. The petiole is
continued up into the lamina as a very broad and thick
midrib, which in the sporiferous leaves (sporophylls) is
continued into the peculiar elongated spike which bears the
sporangia.

The petiole if cut across shows a number of vascular
bundles arranged in a single row, nearly concentric with the
periphery of the section. As these enter the lamina they
anastomose and form a network with elongated meshes (Fig.
114, C) and no free ends. Sections of the spike cut parallel
to its broad diameter show a somewhat similar arrangement of
the vascular bundles, but here there are free branches extending
between the sporangia. The relations of the bundles of the
fertile and sterile parts of the leaf are best followed in the

Fig. xia« — Ophioglossum pendulum (L.X A, Leaf with sporangiophore, natural size; B, cross*
section of the petiole, X 6 ; C, section of the sporangiophore, parallel to its broad surface X 6.

230

MOSSES AND FERNS

CHAP.

smaller species. Prantl ^ describes it as follows for O. Lusitani-
cuffty and states that it is essentially the same in other species.
" The primary bundle given off from the stem branches just after

it enters the petiole. The
main bundle gives off
two smaller lateral
branches right and left.
The latter branch again
near the base of the spor-
angiophore, and the upper
branches from each unite
to form the single bundle
that enters the latter."

The sporangia are
large cavities sunk in the
tissue of the sporophyll,
and scarcely projecting
at all above the surface,
where the position of each
one is indicated by a
faint transverse furrow
which marks the place
where it opens. Seen in
sections parallel to the flat
surface these appear per-
fectly round, but in trans-
verse section are kidney-
shaped (Fig. 121, C).

The apex of the stem
forms a blunt cone, which,
however, is not visi^Je
from the outside. A
longitudinal section
through the end of the
stem shows that it is
covered by a sheath com-
posed of several layers of
cells, and this encloses a
cavity in which are the growing point of the stem and the
youngest leaf. The leaves here form much more rapidly than

1 Prantl (7), p. 155.

FiGk 113. — Ophioghssum vulgatum (L.), X i.

VIII

THE PTERIDOPHYTA—OPHIOGLOSSACEjE

231

in the species of the temperate regions, as the growth continues
uninterruptedly throughout the year. The real apex of the
stem forms an inclined nearly plane surface, slightly raised in
the centre, where the single apical cell is placed (Fig. 115, A,
B). This cell is by no means conspicuous, and not always
readily found, but probably is always present. It has the
form of an inverted three-sided pyramid, but the lateral faces
are more or less strongly convex, and the apex may be trun-
cate. From the few cases
observed it is not possible
to say whether in addition
to the three sets of lateral
segments basal segments
are also formed, but it is
by no means impossible that
such is the case. According
to recent investigations of
Rostowzew^ the apical cell
of the stem of Ophtoglossum
vulgatum shows consider-
able variation, and may be
either a three or four-sided
prism, i£, it apparently also
may have the base truncate.
Holle's^ description agrees
with this except that he
states that he always found
the cell pointed below, not
truncate. The segments
cut off from the lateral
faces are large, and the
divisions irregular. They
are apparently formed in
very slow succession, and
divisions in the segments themselves soon makes it impossible
to trace their limits. Each segment apparently gives rise to a
leaf, but this is impossible to determine with certainty! The
first wall in the young segment probably divides it into an
inner and outer cell, but the next divisions could not be deter-
mined positively. Probably, as in Botrychium, the outer cell is
1 Rostowzew(i), p. 45»- * ^o^le (i).

Fig. 1 14. — Ophioghisum pendulum (L.). A, Median
longitudinal section of stem apex, x 4 ; jt, the
growing point ; B, young sporophyll, X a ; j^,
the sporangiophore ; C, an older leaf, showing
the venation, X 3.

the irregularity of the succeeding

232

MOSSES AND FERNS

next divided by a vertical wall, perpendicular to the broad
faces of the segment, into two cells, in which divisions then
take place in both transverse and longitudinal direction without
strict regularity.

The stem is mostly made up of thin-walled parenchyma,
and the vascular bundles are much less developed than is the
case in the underground stem of O. vulgatum or Botrychiufn.
The bundles are of the collateral form, ix. the inner side is
occupied by the xylem, the outer by the phloem, and there

Fig. 11$.— Ophioglossum pendulum (L.). A, Longitudinal section of stem apex, x6o; B, the central
part of the same section, X x8o ; D, longitudinal section of very young sporangiophore, X i8o ; £«
cross-section of young sporangiophore, x6o.

is no bundle -sheath developed. The bundles form a very
irregular wide-meshed cylinder, not differing essentially from
that in O, vulgatum.

The young leaf is completely concealed by the sheath
formed by the base of the next older one. It is at first a
conical protuberance arising close to the stem apex, around
which its base gradually grows and forms the sheath about it
and the next leaf rudiment. It is probable that here, as in
O. vulgatum} the young leaf grows at first by a definite apical

* Rostowzew (i). p. 451.

THE PTERIDOPHYTA—OPHIOGLOSSACEjE

233

cell. After the plant has reached a certain age, each leaf gives
rise to a sporangial spike, which becomes evident while the leaf
is still very small. The first indication of this is a conical
outgrowth upon the inner surface of the leaf, about halfway
between the apex and base. A longitudinal section of this
shows it to be made up of large cells, especially toward the
top ; but although there was sometimes an appearance that
indicated the presence of a single apical cell, this was by no
means certain, and if there is such an initial cell, its divisions
must be very irregular.

The subsequent growth of the leaf is for a long time mainly
from the base, and the young
sporangial spike is much nearer
the apex in the next stage (Fig.
114, B). No distinct petiole
has yet developed, but the centre
of the young leaf, up to the
point of attachment of the spike,
is traversed by the thick mid-
rib, above which the lamina is
still very small. The young
spike now forms a beak-shaped
body curving inward and up-
ward, and sections of slightly
older stages than the one
figured show the first indications
of the developing sporangia.
Later still the base of the leaf
becomes narrowed into the
petiole, and the spike also becomes divided into the upper
sporiferous portion and the short slender pedicel.

The anatomical structure of the leaf is extremely simple.
The epidermis is composed of rather thick-walled cells, irregularly
polygonal in outline, with large stomata at intervals, about which
the cells are arranged concentrically, and frequently with a good
deal of regularity. The stomata themselves (Fig. 116), seen
from above, have an angular outline, but from below are perfectly
oval, and cross-sections show that this appearance is due to a
partial overarching of the guard cells of the stoma by the
surrounding epidermal cells. The upper walls of the guard
cells are thickened irregularly, giving them the appearance of

Fig. X 16.— Stoma from the leaf of O^ioghssum
Ptndulum^ xa6o.

234

MOSSES AND FERNS

CHAP.

being folded longitudinally. There is 'no distinct hypoderma
formed, and the bulk of the leaf is made up of a uniform meso-
phyll composed of nearly globular cells with much chlorophyll,
and separated by numerous intercellular spaces. In the petiole
the tissues are similar, but more compact, and the walls of the
ground tissue are all deeply pitted. The vascular bundles are
nearly circular in section and show a compact mass of tracheary
tissue (Fig. 1 1 7, /), surrounded by nearly uniform cells with

tcP^

Fig. 117. — Vascular bundle of the petiole otO. ^endnium, X 260 ; /, /, the xylem of the bundle.

moderately thick colourless walls. The limits of the bundle
are not, as in the higher Ferns, marked by a distinct bundle-
sheath, but are indicated simply by the somewhat smaller size
of the cells of the bundle itself — indeed it is not always easy
to say exactly where the ground tissue begins. The xylem is
composed of pointed tracheids whose walls are marked with
thick reticulate bands. This mass of tracheary tissue is situated
near the inner side of the bundle, which like that of the stem is
collateral. The rest of the bundle is composed of sieve-tubes

THE PTERIDOPHYTA—OPHIOGLOSSACE^

235

mingled irregularly with smaller cambiform cells. Whether or
not sieve-tubes occur upon the inner side of the bundle could
not be positively determined. The sporangiophore has much
the same anatomical structure as the rest of the leaf, but stomata
are quite absent from its epidermis. In this respect O. pendulum
differs from O, vulgatum and allied species, where stomata are
developed upon the sporangiophore as well as upon the rest of
the leaf.

The Root

The roots are formed singly near the bases of the leaves,
and are light yellowish brown in colour, and so far as could be

f\o.\\^*—OpkU>glossumptHdul%m{X^). A, Longitudinal ; B,transversesections of the root apex, xaxs*

seen, entirely unbranched. Sections show that here, as in most
vascular plants, the growing point of the root is not at the apex,
but some distance below and protected by the root-cap. The
growth of the root in Ophioglossum can be traced to a single
apical cell (Fig. 1 1 8), which is of large size, and, like that of
the stem, approximately pyramidal in form. While the divi-
sions show greater regularity than in the stem, still they are
very much less so than in the higher Ferns. Segments are
here cut off not only from the lateral faces of the apical cell,
but also from its outer face. These outer segments help to
form the root -cap, which, however, is not derived exclusively
from these, but in part also from the outer cells of the lateral

236

MOSSES AND FERNS

CHAP.

segments. Each of the latter is first divided by a nearly-
vertical wall, perpendicular to its broad faces, into two " sextant
cells," but beyond this no regularity could be disfcovered in the
order of division in the segments, and the tissue at the growing
point, especially in longitudinal section, presents a very confused
arrangement of the cells. A little lower down two regions are
discernible, a central cylinder (plerome), whose limits are not
very clearly defined, and the periblem or cortex. A definite
epidermis is not distinguishable.

The first permanent tissue in the plerome cylinder, which

is elliptical in section,
arises in the form of
small tracheids near the
foci of the elliptical sec-
tion. From here the
formation proceeds to-
wards the centre, and in
the full-grown root the
tracheary tissue forms a
continuous band occupy-
ing the larger axis of
the section, the last-
formed tracheids being
the largest. On either
side of this tracheary
plate is a poorly de-
fined mass of phloem,
similar to that of the
stem and leaf bundles.
Here also no bundle-
FiG. 119.— Vascular bundle of the root of o./^«;«/irw, X 85. sheath is present, and

the limits of the bundle
are not clearly defined. In O. vulgatum the bundle of the root
is diarch to begin' with, but by the suppression of one of the
phloem masses it becomes monarch.

The development of the sporangium has been studied by
Goebel ^ in O, vulgatum, and recently by Bower ^ in this species
and in O, pendulum. The latter has been carefully examined
by the writer, and the results confirm that of the latter investi-
gator, except that it seems possible that the archesporium may

* Goebel (17), p. 390. * Bower (14).

THE PTERIDOPHYTA-^OPHIOGLOSSACE^

237

be traced to a single cell, as Goebel asserts is probably the case
in O. vulgatum,

A transverse section of the very young sporangiophore is
somewhat triangular, the broader side corresponding to the
outer surface of the sporangiophore. The cells are very irre-
gular in form, and no differentiation of the tissues is to be
observed. Sections of somewhat older stages show in some
cases, at least, a large epidermal cell occupying nearly the
centre of the shorter sides of the triangular section. This cell
has a larger nucleus than its neighbours, and is decidedly broader.

Fig. ia<x— a, Very young ; B, older sporangia of O. pendulum ; transverse sections, xa6o.

The next stage was not observed, but a somewhat more advanced
one shows a small group of inner cells (shaded in the figure),
which appear to have arisen from the primary cell by a trans-
verse wall, although this point is exceedingly difficult to deter-
mine on account of the great similarity of all the cells (Fig.
1 20). This group of inner cells (or the single one from which
they perhaps come) constitutes the archesporium, and by rapid
division in all directions forms a large mass of cells whose
contents become denser than those of the surrounding ones,
between which and these, however, the limits are not very plain.
Later, when the number of cells is complete, the difference

238

MOSSES AND FERNS

between them and the sterile tissue of the sporangiophore is
much more evident.

The cells lying outside of the archesporium divide rapidly
both by longitudinal and transverse walls, and form the thick
outer wall of the sporangium. In longitudinal sections, two
rows of cells may be seen extending from the mass of arche-
sporial cells to the periphery. In these rows the vertical walls
have been more numerous than in the adjacent ones, so that

Fig. I2Z. — Ophioglossum pendulum (L.). A, Young sporangium in longitudinal section, X325. Tbe
archesporial cells are shaded, the double line of cells show$ where the sporangium opens ; B, part
of the sporogenous tissue from an older sporangium, X 235 ; C, cross-section of a nearly full-grown
sporangiophore, X15.

the number of cells in these rows is greater. It is between
these rows of cells that the cleft is formed by which the ripe
sporangium opens. The cells of the ground-tissue adjoining
the archesporium divide into several layers of narrow cells,
which form the " tapetum."

After the full number of cells is reached in the archesporium,
their walls become partially disorganised, and the cells round

VIII THE PTERIDOPHYTA—OPHIOGLOSSACE^ 239

off and separate, exactly as in the sporogonium of a Bryophyte,
and each cell is, potentially at least, a spore mother cell.
Bower ^ states that only a part of the cells produce spores, and
that the rest remain sterile and serve with the disorganised
tapetal cells to nourish the growing spores. The final division
of the spore mother cells into four spores is identical with that
of the Bryophytes.

At maturity the sporangium opens by a cleft, whose position
is indicated as we have seen in the younger stages, and as the
cells shrink with the drying of the ripe sporangiophore the
spores are forced out through this cleft.

Ophioglossum vulgatum and the other terrestrial forms show
some points of difference when compared with O. pendulum.
These grow much more slowly, and longitudinal sections of the
upper part of the subterranean stem show several leaves in
different stages of development. Each leaf rudiment, as in
0. pendulum^ is covered by a conical sheath, formed at the base
of the next older leaf, and these sheaths are open at the top, so
that there is direct communication between the outside air and
the youngest of these sheaths which encloses, as in the latter
species, the youngest leaf rudiment and stem apex.^ In these
terrestrial forms, also, the sporangiophore is longer stalked, and
the lamina of the leaf more clearly separated from the petiole,
which is not continued into it. The lamina is relatively broader
and the venation more complex, in some species showing also
free endings to the ultimate branches. The sporangia, too,
project more strongly and are very evident (Fig. 113). Branch-
ing of the roots occurs occasionally, and according to Rostowzew ^
may be either spurious or genuine. In the first place an
adventive bud, which ordinarily would develop into a stem,
develops a single root and then ceases to grow. This root
appears to be formed directly from the main root, and as the
latter continues to grow the effect is that of a true dichotomy.
The latter does occur, but not frequently.

The formation of adventitious buds upon the roots is the
principal method of propagation of some species of Ophioglossum y
whose prothallia, as we have seen, are apparently very seldom
developed. Rostowzew states that these are not developed
from the apical cell of the root, but arise from one of the
younger segments, and the apical cell is produced from one of

' Bower (14). ' Rostowzew (i), p. 451. ' Rostowzew, Ic,

240 MOSSES AND FERNS chap, viii

the outer cells of the young segment, but is covered by the
root-cap, through which the bud afterwards breaks. The sheath
covering the first leaf of the bud is formed from the cortex of
the root and the root-cap.

Differing most widely from the other species in general
appearance is the curious epiphytic O, {Cheiroglossd) pcdmatum.
In this the leaf is dichotomously branched, and instead of a
single sporangiophore there are a number arranged in two rows
along the sides of the upper part of the petiole and the base of
the lamina.

The genus Botrychium includes several exceedingly variable
species, the simplest forms, like B, simplex (¥\g. 1 22, A, B), being
very close to Ophioglossum^ while leading from these is a series
ending in much more complicated types, of which B, Virginianum
is a good example. In B. simplex the lamina of the leaf is
either entirely undivided, as in most species of Opkioglossum, or
once pinnatifid. From this there is a complete series to the
ample decompound leaf of B, Virginianum. When the other
parts of the plant are studied we find that this greater com-
plexity extends to these as well. Thus the sporangiophore is
also decompound, and the sporangia entirely free, and showing
an approach to that found in such Ferns as Osmunda, and the
dichotomous venation of the simpler forms approaches the
pinnate type in B, Virginianum. The tissues, especially the
vascular bundles, are also more highly differentiated in these
species.

Under favourable conditions well-grown plants of B. Vir-
ginianum reach a height of 50 cm. or more, and the sterile
lamina of the leaf, which is triangular in outline, may be
30 to 40 cm. in breadth, and from three to four times pinnate.
The texture of the leaf is membranaceous and not fleshy like
that of Ophioglossum and most species of Botrychium. The
sporangiophore is twice or thrice pinnate. The plant sends up
a single leaf each year from the underground stem, which is
upright and several centimetres in length in old specimens.
The roots are thick and fleshy, and much smaller at the point
of insertion. As in Ophioglossum each root corresponds prob-
ably to a leaf, but the roots branch frequently, so that the root
system is much better developed than in Ophioglossum. The
secondary roots of B. Virginianum arise laterally, and in much
the same way as those of the higher Ferns. As in the terres-

Fig. 122.— a, B, Bottyckium simplex (Hitch), natural sire; C, B, Umatum (Sw.), x|; D, leaf
segment oi B, lunaria (Sw.) ; £, leaf segment of B^ Virginianum (Sw.), natural size ; F, portion
of sterile leaf segment oi Helmintkosiachys Zeylanica (Hk.) ; G, fragment of the sporangiophorc
of the same enlarged. A, B, C after Luerssen ; D, F after Hooker.

242

MOSSES AND FERNS

trial species of Ophioglossum^ the development of the leaves is
very slow.

In most species of Botrychium the relation of the leaf base
to the young bud and stem apex is the same as in Ophioglossunt^
except that the sheath is more obviously formed from the leaf
base ; but in B. Virginianum the sheath is open on one side,
and more resembles a pair of stipules. Fig. 123, A shows the
stem and terminal bud of a plant of this species with all but

Fig. 123. — Botrychium Viiy;iHianum (Sw.). A, Rhizome and terminal bud of a strong plant, the roots
and all but the base of the oldest leaf removed, X i ; B, longitudinal section of the bud, x 3 : x/, the
stem apex ; I. II. III., the leaves ; C, transverse section of the petiole, X4 ; D, transverse section
of the rhizome, X about 16 ; P, the pith ; m, medullary rays ; .r, xylem ; c, cambium ; /I,
phloem ; M, endodermis.

the base of the leaf of the present year cut away, and B the
same with the bud cut open longitudinally. At this stage the
parts of the leaf for the next year are well advanced, and the
formation of the individual sporangia just begun. The leaf for
the second year already shows the sporangiophore clearly
evident, and the leaf which is to unfold in three years is
evident, but the sporangiophore not yet differentiated. At the
base of the youngest leaf is the stem apex. The whole bud
is covered in this species with numerous short hairs, which are

VIII THE PTERIDOPHYTA—OPHIOGLOSSACEM 243

also found in B, ternatum and some other species, but in B,
simplex and the other simpler species it is perfectly smooth, as
in Ophioglossum, The young leaves in B, Virginianum are
bent over, and the segments of the leaf are bent inward in a
way that recalls the vernation of the true Ferns. The spor-
angiophore grows out from the inner surface of the lamina,
and its branches are directed in the opposite direction from
those of the sterile part of the leaf.

The vascular bundles of the stem are much more
prominent than in Ophioglossum^ and form a hollow cylinder,
with small gaps only corresponding to the leaves. This
cylinder shows the tissues arranged in a manner that more
nearly resembles the structure of the stem in Gymnosperms
or normal Dicotyledons than anything else. Surrounding the
central pith (Fig. 123, P) is a ring of woody tissue {x) with
radiating medullary rays {m\ and outside of this a ring of
phloem, separated from the xylem by a zone of cambium {c\
so that here alone among the Ferns the bundles are capable
of secondary thickening. The whole cylinder is enclosed by
a bundle -sheath (endodermis) consisting of a single layer of
cells. ^

The cortical part of the stem is mainly composed of
starch-bearing parenchyma, but the outermost layers show a
formation of cork, which also is formed in the cortical portions
of the roots.

The free surface of the stem apex is very narrow, and the
cells about it correspondingly compressed. The apical cell
(Fig. 1 24, A, B), seen in longitudinal section, is very deep and
narrow, but as comparison of cross and longitudinal sections
shows, has the characteristic pyramidal form, and here there
is no doubt that only lateral segments are cut off from it.
Holle's ^ figure of Botrychium rutcefolium closely resembles B,
Virginianum^ and probably the other species will show the
same form of apical cell. The divisions are decidedly more
regular in the segments of B, Virginianum than in Opkio-
glossum^ and can be more easily followed, although here, too,
as the division evidently proceeds very slowly, it is difficult to
trace the limits of the segments beyond the first complete set,
which in transverse section are sufficiently clear. The first
division divides the segment into an inner and an outer cell,

» Holle (I), PI. IV. Fig. 32.

244

MOSSES AND FERNS

the former probably being directly the initial for the plerome
cylinder. The outer cell by later divisions forms the cortex,
and the epidermis which covers the very small exposed surface
of the stem apex. Here, as in Ophioglossum^ it is impossible
to determine exactly the method of origin of the young leaves,
one of which probably corresponds to each segment of the
apical cell, but as soon as the leaf can be recognised as such
it is already a multicellular organ. It grows at first by an
apical cell which seems to correspond closely in its growth
with that of the stem. From almost the very first (Fig. 124)

Fig. xz^^Bottychium Virginianum (Sw.). A, Longitudinal section of the stem apex of a young
plant, X 260 ; B, cross-section of a similar specimen ; L, the youngest leaf.

the growth of the leaf is stronger on the outer side, and in
consequence it bends inward over the stem apex.

The arrangement of the tissues of the fully -developed
stem shows, as we have seen, a striking similarity to those
in the stems of many Spermaphytes. The xylem of the
strictly collateral bundle is made up principally of large
prismatic tracheids (Fig. 125), whose walls are marked with
bordered pits not unlike those so characteristic of the Coni-
ferae, but somewhat intermediate between these and the
elongated ones found in most Ferns. The walls between
the pits are very much thickened, and the bottoms of

THE PTERIDOPHYTA—OPHIOGLOSSACEjE

245

corresponding pits in the walls of adjacent tracheids are
separated by a very delicate membrane. At intervals
medullary rays, one cell thick, extend from the pith to the
outer limit of the xylem. The cells are elongated radially,
and have uniformly thickened walls and granular contents.

The phloem consists of large sieve -tubes and similar but
smaller parenchymatous cells. No bast fibres or sclerenchy-
matous cells are present. The whole cylinder is bounded by
a single layer of cells somewhat compressed radially, forming

Fio. 125.— A, Part of a cross-section of the stem bundle of B. VirgimoMum^ x aoo.— lettering as in
Fig. 133 ; B, a portion of the tracheary tissue, showing the peculiarly pitted walls, X400.

the endodermis or bundle -sheath. Between the xylem and
phloem is a well-defined layer of cambium by whose growth
the thickness of the vascular cylinder is slowly but constantly
added to, and as a result there is a secondary growth of the
stem strictly comparable to that of the Dicotyledons.

The outer layer of the cortex (the epidermis is quite
absent) develops cork, but not from a definite cork cambium.^
These cork cells arise by repeated tangential divisions in cells

» Holle(i), p.249.

246

MOSSES AND FERNS

CHAP.

near the periphery, and have in consequence the same regular
arrangement seen in similar cells of the higher plants.

A cross-section of the petiole of the earliest leaves of the
young plant show but a single nearly central vascular bundle,
but as the plant grows older the number becomes much larger,
and may reach ten.^ In leaves of moderate size there are
usually about four, and these are arranged symmetrically.
The ground tissue is composed mainly of large thin-walled
parenchyma and a well-marked epidermis. The fibrovascular

Fig. 126.— Part of a vascxilar bundle from the petiole of B. Virg^nianuftt, X245; xy^ xylem; /*,
phloem ; j,*, sieve-tubes ; B, two sie\'e-tubes in longitudinal section, X4go ; */, sieve-plates ; n, nuclei.

bundles are arranged in two groups, right and left, and where
there are four of them the inner ones are the larger, and in
cross-section crescent -shaped. The xylem here occupies the
middle of the section, and is completely surrounded by the
phloem, ue. the bundle is concentric, like that of the true Ferns.
In B. lunaria the bundle has the phloem only perfectly
developed on its outer side and approaches the collateral form.
B. tematum and B. lunaria^ while having concentric bundles,

1 Luerssen (8), p. 588.

VIII THE PTERIDOPHYTA—OPHIOGLOSSACE^ 247

also have the phloem more strongly developed on the outer
side. The tracheary tissue is much like that of the stem, but
the tracheids are smaller and the walls thinner.

The phloem is composed also of the same elements, large
sieve-tubes, arranged in a pretty definite zone next the xylem,
and smaller cells of similar appearance, but not showing the
multinucleate character or perforated transverse walls of the
latter. The sieve-tubes are large (Fig. 1 26), and in longitudinal
section are seen to consist of rows of wide cells with either hori-
zontal or oblique division walls. The transverse walls separating
two members of a sieve-tube are somewhat swollen and show
small perforations, which are not always easily demonstrated.
According to Janczewski^ these pits do not penetrate the
membrane between the cells, but Russow's* assumption that
there is direct communication between the cells is correct,
although difficult to prove. Russow also states that callus is
present in the sieve -plates of Botrychiunty although poorly
developed. According to Janczewski' the pores are not
confined to the transverse walls, but may also occur, but much
less frequently, in the longitudinal walls. The contents of the
sieve -tubes consist of a thin parietal layer of protoplasm in
which numerous nuclei are imbedded. Little glistening
globules are also found, especially close to the openings of the
pores of the sieve-plates.

The lamina of the sterile segment of the leaf is composed
of a spongy green mesophyll, more compact on the upper
surface. The epidermal cells show the wavy outlines char-
acteristic of the broad leaves of other Ferns, and develop
stomata only upon the lower side of the leaf

The Root

The roots arise singly at the bases of the leaves, and in
older plants branch monopodially. Like those of Ophioglossum
they have no root-hairs, but the smooth surface of the younger
roots becomes often strongly wrinkled in the older ones.
Sections either transverse or longitudinal, through the root tip,
when compared with those of Ophioglossum^ show a very
much greater regularity in the disposition of the cells. This
IS less marked in B. tematum, and probably an examination
' Janczewski (4). • Russow (5). ' Janczewski (4), p. 69.

248

MOSSES AND FERNS

CHAP.

of such forms as B, simplex will show an approximation to the
condition found in Opkioglossum^ although Holle's^ figure of
B, lunaria shows even greater regularity in the arrangement of
the apical meristem than is found in B. Vtrginianum. A
careful examination of this point is much to be desired.

The first wall in the young lateral segment is the sextant
wall, as in the higher Ferns, and divides the segment into two
cells of unequal depth. The next wall divides the larger of these
cells into an inner and an outer one, the former becoming the
initial of the central plerome cylinder, the outer one, together
with the whole of the smaller semi-segment, giving rise to the

Fig. \rj,—Botrychium Virginianum (Sw.). A, Longitudinal ; B, transverse sections of the root apex,

X9oo; //, plerome.

cortex, in which the divisions are very similar to, but some-
what less regular than in Equisetum and the leptosporangfiate
Ferns. As usual in roots of this type segments are also cut
off from the outer face of the apical cell, but I have never seen,
either in B. Virginianum or B. ternatum^ any indication that
the growth of the root -cap was due exclusively to the
development of these segments, as Holle states both for B.
lunaria and Ophioglossum vulgatum. In both species of
Botrychium examined by me the growth of the root-cap was
evidently due in part to the division of cells in the outer part
of the lateral segments, so that in exactly median sections

1 Holle (I).

VIII THE PTERIDOPHYTA—OPHIOGLOSSACEyE 249

there was not the clear separation of the root -cap from the
body of the root that is so distinct in Equisetum^ for example.

The central fibrovascular cylinder of the root is not provided
with a definite endodermis, and its limits are not clearly
defined. It varies in the number of xylem and phloem
masses, even in the same species. In B. Virginianum the
larger roots show three or four xylem masses (Fig. 128). B.
ternatum has a usually triarch bundle, while B, lunaria is
commonly diarch.^ The elements both of the xylem and

Fig. 128.— Tetrarch vascular bundle of the root o{ B. VirginioHum^ X85.

phloem are much like those in the stem and do not need
any special description. The roots increase considerably in
diameter as they grow older, but this enlargement does not
take place at the base, where the root is noticeably constricted.
The enlargement is due entirely to the cortical tissue, and is
mainly simply an enlargement of the cells. The diameter of
the central cylinder remains the same after it is once formed.
In the outer part of the root, as in the stem, there is a develop-
ment of cork.

» Holle(i), p.245.

250 MOSSES AND FERNS chap.

The Sporangium

In the simplest forms of B. simplex the sporangia, which
are much larger than those of B, Virginianumy form two ro\*'s
very much as in Ophioglossum ; but in all the more complicated
forms the sporangiophore branches in much the same way as
the sterile part of the leaf, and the ultimate segments become
the sporangia. In ^. Virginianum the development of the
individual sporangia begins just about a year previous to their
ripening, and if the plants are taken up about the time the
spores are shed, the earliest stages may be found. The
sporangiophore is at this time thrice pinnate in the lai^er
specimens, and an examination of its ultimate divisions will
show the youngest recognisable sporangia. These form slight
elevations growing smaller toward the end of the segment
(Fig. 129), and exact median sections show that at the apex of
the broadly conical prominence which is the first stage of the
young sporangium there is a large pyramidal cell with a
truncate apex. Holtzman^ thinks the sporangium may be
traceable to a single cell, and that the divisions at first are like
those in a three-sided apical cell. I was unable to satisfy
myself on this point, but the youngest stages found by me in
which the sporangial nature of the outgrowths was unmistakable,
would not forbid such an interpretation, although there was no
doubt that the basal part of the sporangium is derived in part
from the surrounding tissue.

From the central cell, by a periclinal wall, an inner cell,
the archesporium, is separated from an outer one. The outer
cell divides next by cross walls, and this is followed by similar
divisions in the inner cells (Fig. 129). The succeeding divi-
sions in the outer cells are now mainly periclinal, and transform
the four cells lying immediately above the archesporium into
as many rows of tabular cells. Growth is active in the
meantime in the basal part of the sporangium, which projects
more and more until it becomes almost spherical. To judge
from the somewhat incomplete account given by Goebel* of
B. lunariay this species corresponds closely in its early stages
to that of B, Virginianum. The later divisions in the arche-
sporium do not apparently follow any definite rule, but divi-

1 Holtzman (i). « Goebel (3).

THE PTERIDOPHYTA—OPHIOGLOSSACE/E

251

sions take place in all directions until a very large number
of cells is formed. The cells immediately adjoining the
sporogenous tissue divide into tabular tapetal cells, as in
Ophioglossutn, The sporangium shortly before the isolation
of the spore mother cells (Fig. 129, C) is a nearly globular
body with a thick, very short stalk. The central part of the
upper portion is occupied by the sporogenous tissue sur-
rounded by a massive wall of several layers of cells, of which
the inner ones constitute the tapetum. The central cells, as

Fig. t^.—Botrychium VirginianMm (Sw.X Development of the sporangia. A, i, 2, Very young
sporangia ; B, a somewhat older one, X 480 ; C, older sporangium, X 340, all median longitudinal
sections, the sporogenous cells have the nuclei shown.

usual, have larger nuclei, and more granular contents than the
outer ones. The stages between this and the ripe sporangium
were not seen, so that it cannot be stated positively whether all
the cells of the sporogenous tissue (which seems probable) or
only a part of them, as in Ophioglossutn^ develop spores.

The stalk is traversed by a short vascular bundle, which is
first evident about the time that the number of sporogenous
cells is complete, and joins directly with the young vascular
bundre of the leaf segment (Fig. 129, C). The ripe sporangium
opens by a transverse slit, as in Ophioglossutn,

252 MOSSES AND FERNS chap.

/ The presence of fungous filaments in the roots of the
Ophioglossaceae has been repeatedly observed, and has been
the subject of recent investigations by Atkinson,^ who is inclined
to regard them as of the same nature as the mycorrhiza found
in connection with the roots of many Dicotyledons, especially
Cupuliferae. Atkinson asserts that he finds them invariably
present in all the forms he has examined ; but Holle * states
that, while they are usually present in Ophioglossum^ he has
found strong roots entirely free from them, and that in
Botryckium rutcefolium they were mainly confined to the diarch
roots, and that this is connected with a weakening of the growth
of the root through the growth of the fungus, by which the
triarch bundle of the normal fully-developed root is replaced by
the diarch form of the weaker one.

The third genus of the Ophioglossaceae, Helminthostachys,
with the single species H, Zeylanicay is in some respects inter-
mediate between the other two, but differs from both in some
particulars. The sporophyte, which alone is known, and that
very imperfectly, has a creeping fleshy subterranean rhizome,
with the insertion of the leaves corresponding to Ophioglossum
pendulum. According to PrantI,* who has made a somewhat
careful study of a plant, the roots do not show any definite
relation to the leaves, as Holle claims is the case in the other
genera. The plant sends up a single leaf, which may reach a
height of 30 to 40 cm. or more, and as in the Ophioglossum
vulgatum and B. Vtrgimanum, the sporangiophore arises from
the base of the sterile division of the leaf. The latter is
palmately lobed, and the primary divisions are also divided
again. Often the primary divisions are temately arranged, as
in the larger species of Botrychium. The venation is different
from that of the other Ophioglossaceae, and is extremely like that
oi Angiopteris, Each pinnule is traversed by a strong midrib,
from which lateral dichotomously branched veins run to the
margin. In regard to the structure of the sheath that encloses
the young leaf and stem apex, Helminthostachys resembles
Ophioglossum.

Prantl * states that the vascular cylinder of the stem is solid
on the lower surface, but on the upper side has the openings
corresponding to the leaf insertions. Two primary bundles
are formed for each leaf, which fork before they enter the petiole,

* Atkinson (2). « Holle (i). » Prantl (7). < Prantl, /.r.

viii THE PTERIDOPHYTA—OPHIOGLOSSACE^ 253

so that there are four bundles at the base of the petiole.
Higher up a cross-section shows ten bundles arranged about
the periphery, and an inner one, formed by the branching of
one of the others upon the upper side. This inner bundle,, and
those of the upper side of the stalk, furnish the bundles for the
sporangiophore.

The sporangiophore is long-stalked and in general appear-
ance intermediate between that of the other genera, but a
careful examination shows that it is much more like that of
Botrychium, It is pinnately branched, but in an irregular way,
and the small branchlets bear crowded oval sporangia, which
open longitudinally on the outer side, and not transversely as
in the other genera. The tips of the branches, instead of
forming sporangia as in Botrychium^ develop into green leaf-
like lobes, which upon the shorter branchlets are often arranged
in a rosette of three or four together, with the sporangia close
below them (Fig. 122, D). This at first sight looks as if the
sporangia were produced upon the lower side of these, like
Equisetum^ but a very slight examination shows at once that
this is only apparent, and the sporangia are undoubtedly
outgrowths of the branches as in Botrychium, The green lobes
are seen to be 6nly the vegetative tips of the branches, or
perhaps better comparable to such sterile leaf segments as are
not uncommon in Osmunda Claytoniana,

Unfortunately the life history is absolutely unknown, and
its histology is also too imperfectly known to make it possible
at present to determine its exact relation on the one hand to
the other Ophioglossaceae, and on the other to the Marattiaceae
and Filices.

CHAPTER IX

MARATTIACEiE — ISOETACEiE

The MarattiacecB

The Marattiaceae at the present time include four genera with
about twenty-five species, confined exclusively to tropical regions.
In a fossil condition they are much more numerous and
diversified, and according to Solms-Laubach ^ comprise the
majority of the carboniferous and pre-carboniferous Ferns.

Recently a good deal of attention has been paid to these
Ferns, and our knowledge of their life-history and structure is
fairly complete. Some of them are Ferns of gigantic size.
Thus the stem of Angiopteris evecta is sometimes nearly a metre
in height and almost as thick, with leaves 5 to 6 metres in length,
and some species of Marattia are almost as large. The other
genera, Kaulfussia and Danceay include only species of small or
medium size. While in the structure of the tissues and the
character of the sporangia these show resemblances to the
Ophioglossaceae, their general appearance is more like that of
the true Ferns, with which they also agree in the circinate
vernation of their leaves. The sporangia are borne upon the
lower surface of ordinary leaves, as in most leptosporangiate
Ferns, but the sporangia themselves are very different, and are
more or less completely united into groups or synangia, which
open either by longitudinal slits or, in Dancea^ by a terminal
pore. The base of the leaf is provided with a pair of fleshy
stipules, which possibly correspond to the sheath at the base of
the petiole in Botrychium,

* Solms-Laubach (2), p. 142.

CHAP. IX MARATTIACE^'-ISOETACEM 255

Tfie Gametophyte

The germination of the spores and development of the
prothallium were first investigated by Luerssen ^ and Jonkman *
in Angiopteris and Marattia^ and later by the latter investigator
for Kaulfussia?

The spores are of two kinds, bilateral and tetrahedral, but
the former are more common. They contain no chlorophyll,
but oil is present in drops of varying size, as well as other
granular bodies. The nucleus occupies the centre of the spore
and is connected with the wall by fine protoplasmic filaments.
The wall of the spore is colourless and shows three coats, of
which the outer one (perinium) is covered with fine tubercles.

Germination begins within a few days and is first indicated
by the development of chlorophyll. This does not, as Jonk-
man * asserts, first appear in amorphous masses, but very small,
faintly-tinted chromatophores appear between the large oil-
drops, and these rapidly increase in size and depth of colour
as germination proceeds, and their number increases by the
ordinary division. In the bilateral spores the exospore is
burst open above the thickened ventral ridge found in these
spores, and the growing endospore slowly protrudes through
this. The spore enlarges to several times its original diameter
before the first division occurs, and forms a globular cell in
which the large chloroplasts are arranged peripherally.

The first division takes place about a month after the spores
are sown, and is perpendicular to the longer axis of the cell,
dividing it either into two equal parts, or the lower may be
much smaller and develop into a root-hair. In the former case
€ach cell next divides by walls at right angles to the first, and
the resulting cells are arranged like the quadrants of a circle, and
one of these cells becomes the two-sided apical cell from which
the young prothallium for a long time grows (Fig. 130), much
as in Aneura. This type of prothallium, according to Jonkman,*
is commoner in Marattia than in Angiopteris^ where more
commonly a cell mass is the first result of germination. This
latter is usually derived from the form where a root-hair is
"developed at first. In this case only the larger of the primary

* Luerssen (5). * Jonkman (i). » Jonkman (2).

^ Jonkman, Bot, ZdL 1878, p. 136. ' Jonkman, Lc, p. 146.

256

MOSSES AND FERNS

cells give rise to the prothallium. In the larger cell divisions
take place in three directions and transform it into a nearly
globular cell mass, terminated by four quadrant cells, one of
which usually becomes the apical cell, much as in the flat pro-
thallium. In exceptional cases the first divisions are in one
plane and a short filament results.

As soon as the apical cell is established it grows in pre-
cisely the same way as the similar cell in the thallus of a

Fig. ly^—Angio^teris evtcia (Hoffm). Germination of the spores,— A, B, X 220 ; C, X 175 *, *^y qiore
membrane : Xy apical cell (after Jonkman).

Liverwort, and produces a thallus of much the same form and
structure. As the prothallium grows older, however, a cross-
wall forms in the apical cell, and this is followed by a longi-
tudinal wall in the outer one, forming two similar cells which,
by further longitudinal divisions, may produce a row of marginal
initials, and the subsequent growth of the prothallium is due to
the divisions and growth of this group of initial cells (Fig.
131, A).

At first the prothallium has a spatulate form, but before the

MARA TTIA CE^—ISOE TA CE^E

257

single apical cell is replaced by the group of marginal initials,
the outer cells of the segments grow more rapidly than the
inner ones, and the segments project beyond the apical cell,
which comes to lie in a depression between the two lobes formed
by the outer parts of the segments, and the prothallium assumes
the heart -shape found in most homosporous Ferns. The
secondary initial cells vary in number with the width of the
indentation in which they lie. Seen from the surface they are
oblong in shape, but in vertical section are nearly semicircular
(Fig. 131, B). Basal segments are cut off by a wall that
extends the whole depth of
the prothallium, and the seg-
ment is then divided by a
horizontal wall into a dorsal
and ventral cell of nearly
equal size. The divisions are
more numerous in the ventral
than in the dorsal cells of the
segment, this difference first
being manifest some distance
back of the apex. Owing to
this, a strongly projecting,
nearly hemispherical cushion-
like mass of tissue is formed
upon the ventral surface. The
superficial cells of both sides
of the prothallium have a
well-marked cuticle. Numer-
ous brown root-hairs, which,
like those of the simpler
Liverworts, are unicellular
and thin -walled, grow out

from the cells of the lower surface, especially from the broad
midrib. The full-grown prothallium in Jf. Douglasii is some-
times a centimetre or more in length (Fig. 132), and tapers
from the broad heart-shaped forward end to a narrow base.
In Angiopteris ^ it is more nearly orbicular. In both genera it
is dark-green in colour, looking very much like the thallus of
Anthoceros Icevis^ and like this too is thick and fleshy in
texture. A broad midrib extends for nearly the whole length

^ Farmer (3).
S

Fig. i-^u^Marattia Douglasii (Baker). A, Hon-
zontal section of prothallium apex, with two
initials, X160. B, Longitudinal section of a
similar growbg point; </, dorsal; v, ventral
segment.

258

MOSSES AND FERNS

of the thallus and merges gradually into the wings, which are
also several-layered, nearly or quite to the margin.

The very old prothallia sometimes branch dichotomously
(Fig. 132, B, C), and the process is identical with that in the
thallose Hepaticae. The two growing points are separated by
a median lobe in the same way, and the midrib with the sexual

Fig. t^.—Maraitia Dauglasii {Hsktr), A, Prothallium about one year old, X2 ; B, the lane pro>
thallium about a year later, showing a dichotomy of the growing point ; C, the same seen from
below, showing two archegonial cushions (9); D, prothallium with young sporophyte, X4 : £, «
somewhat older one, seen from the side, X 4 ; r, the primary root.

organs upon it forks with it, exactly as we find, for example,
the antheridial receptacle forking in Fimbriaria Calif omica (Fig.
I, A). Besides this form of branching, which is not common,
adventitious buds are produced upon the margin of the thallus
very frequently. These grow in precisely the same way as the
main prothallium, and after a time may become detached and
form independent plants ; or they may develop sexual organs
(mainly antheridia) while still connected with the mother

IX MARA TTIA CE^-ISOETACE^ 259

plant. The duration of the prothallium is apparently unlimited,
so long as it remains unfecundated. The writer kept prothallia
of Marattia Douglasii for nearly two years, during which they
grew continuously and finally reached a length of over two
centimetres. At the end of this time they were growing
vigorously, and there was nothing to indicate the slightest
decrease in their vitality.

The prothallia are monoecious, although not infrequently
the smaller ones bear only antheridia. The latter always
appear first, and are mainly found upon the lower side of the
midrib, but may also occur upon the upper side. The arche-
gonia are confined to the low6r surface of the midrib, and as
they turn dark brown if they are not fertilised, they are visible
to the naked eye as dark brown specks studding the broad
thick midrib. Both antheridia and archegonia resemble closely
those of the Ophioglossaceai.

The antheridium arises from a single superficial cell which first
divides into an inner cell, from which the sperm cells are derived,
and an outer cover cell (Fig. 133, A). The latter divides by
several curved vertical walls (Figs. E-G) which intersect, and
the last wall cuts off a small triangular cell {p\ which is thrown
off when the antheridium opens, and leaves an opening through
which the sperm cells are ejected. The inner cell, by repeated
bipartitions, gives rise to a large number of polyhedral sperm
cells. Before the full number of these is complete, cells are cut
off from the adjacent prothallial cells, which completely enclose
the mass of sperm cells. As in other Archegoniates, the
nucleus of the sperm cell, after its final division, shows no
nucleolus. The first sign of the formation of the spermatozoid
that could be detected was an indentation upon one side,
followed by a rapid flattening and growth of the whole nucleus.
The cytoplasmic prominence which, according to Strasburger,^
is the first indication of the formation of the spermatozoid,
could not be certainly detected. The main part of the sperma-
tozoid stains strongly with alum-cochineal, and is sharply differen-
tiated against the colourless cytoplasm, and for some time shows
the characteristic nuclear structure. The origin of the cilia was
not very clearly made out, but probably, as Strasburger claims,
they are direct outgrowths of the forward end. The free
spermatozoid (Fig. 133, I) is a flattened band, somewhat blunt

^ Strasburger (ii), vol. iv. p. 116.

26o

MOSSES AND FERNS

CHAP.

behind and tapering to a fine point in front ; attached to a
point just back of the apex are several fine cilia. The bcxiy
shows only about two complete coils.

The youngest archegonia are met with some distance back of
the growing point, and apparently any superficial cell is poten-
tially an archegonium mother cell. The latter divides usually into
three superimposed cells (Fig. 1 34, A), of which the lowest (*)
forms the base of the archegonium. From the central one by a

Fig. i22.—Maruitia DoM£lasii (Baker). Development of the antheridium. A-D, Longitudinal
section, X515 ; E-G, surface views, X257 ; H, ripe sperm cells; I, free sperroatozoids, Xxoja

transverse division are formed the primary neck canal cell and
the central cell. Each of these divides again transversely. In
the upper one this division is often incomplete and confined to
the nucleus ; but in the central cell the division results in the
separation of the ventral canal cell from the ovum. Before the
separation of the primary neck canal cell from the central cell,
the cover cell divides as in the Liverworts into four cells by
intersecting vertical walls, and each of these cells by further

MARA TTIACE^-^-ISOETACEjE

261

obliquely transverse walls forms a row of about three cells, and
these four rows compose the short neck. The canal cells are
very broad and the egg cell small, so that after the archegonium
opens it occupies but a small part of the cavity left by the
disintegration and expulsion of the canal cells. Before the
archegonium is mature, flat cells are cut off from the adjacent
prothallial tissue as in the antheridium (Fig. 1 34, D). The
neck of the ripe archegonium projects but little above the
surface of the prothallium, and in this respect recalls both the

Fig. 134. — Maraitia Dou^ltuii (fiaktx), A-D, Development of the archegonium, X 450 ; E, section of
the fertilised egg, showing the spermatozoid (j/) in contact with its nucleus, X 485 : F, successive
longitudinal sections of a young embryo, X 325 ; ^, ^, the basal wall, the arrow points towards the
archegonium.

lower Ophioglossaceae and the Anthoceroteae. The ripe ovum
is somewhat elliptical, and slightly flattened vertically. Its
upper third is colourless and nearly hyaline. This is the
"receptive spot," , and it is here that the spermatozoid enters.
The nucleus is of moderate size, and not rich in chromatin ; a
small but distinct nucleolus is present. The spermatozoid
retains its original form after it first enters the egg, and until it
comes in contact with the membrane of the egg nucleus. It
afterwards contracts and assumes much the appearance of the

262

MOSSES AND FERNS

nucleus of the sperm cell previous to the differentiation of the
spermatozoid. The two nuclei then gradually fuse, but all the
different stages could not be traced. Before the first division
takes place, however, but one nucleus can be seen, and this
much resembles the nucleus of the unfertilised egg.

After fertilisation the egg enlarges to several times its
original size before dividing. The first (basal) wall is transverse
and is followed in each half by two others, the median and
octant walls. The nearly globular embryo is thus divided into

Fig. 135. — Maraitia Dauglasii (Baker). Embryogeny. A, Longitudinal ; B, transverse sections of
embryos, X 2x5 ; C, vertical section of an older embryo, showing its position in the prothalliam,
X 72 ; stt the stem ; pr^ prothallium ; D, upper part of the same embryo, X 215.

eight similar cells, each having the tetrahedral form of a globe
octant. The next divisions are not perfectly understood, and
evidently are not absolutely uniform in all cases. All the
octants at first show nearly uniform growth, and the embryo
retains its nearly oval form (Figs. 134, F, 135, A). The first
division in the octants is essentially the same, and consists in a
series of anticlinal walls, before any periclinal walls appear, so
that we may say that for a short time each octant has a dis-
tinct apical growth, and there are eight growing points. The

MARA TTIACE^—ISOETACEjE

263

older embryo shows an 'external differentiation into the first
leaf, stem, and root, but the foot is not clearly limited at first.
The basal wall separates the embryo into two regions, epibasal
and hypobasal. From the former the cotyledon and stem apex
are derived, from the latter the root and foot.

The cotyledon arises from the anterior pair of epibasal
octants, which are in the Marattiaceae, unlike all the other Ferns,
turned away from the archegonium opening. In the earliest
stages where the cotyledon is recognisable, no single apical cell
could be made out, and later the growth is very largely basal.
At first the growth 'is nearly vertical, but it soon becomes

Fig. 136. — Maraiiia Douglasti (Jia\xr). A, Cross-section of the young sporopbyte at the junction
of the cotyledon and stem ; si^ the apical meristem of the stem, Xax5 ; B, the stem apex of the
same, X430; C, longitudinal section of the stem apex of a plant of about the same age, X3X5 ; /r,
the primary tracheary tissue ; ^, the second root.

.stronger upon the outer side, and the leaf rudiment bends
inwards. At this stage the different tissues begin to be dis-
tinguishable. Somewhat later the tip of the cotyledon becomes
flattened, and still later there is a dichotomy of this flattened
part which thus forms a fan-shaped lamina (Fig. 138). The
first tissue to be recognised is the vascular bundle, which
traverses the centre of the petiole and at first consists of
uniform thin-walled elongated cells (procambium). This forma-
tion of procambium begins in the centre of the embryo and
proceeds in three directions, one of the strands going into the
cotyledon, one in an almost opposite direction to the primary

264

MOSSES AND FERNS

CHAP.

root, and a very much shorter one to the young stem aj^ex,
which lies close to the base of the cotyledon. The outer layer
of cells of the cotyledon forms a pretty clearly defined epidermis
separated from the axial procambium strand by several layers
of young ground-tissue cells.

The apex of the young stem is occupied in some cases, at

Fig. lyi.^Maraitia Doug^lasii(fis\ivt), A, B, C, Three transverse sections of a root from the young
sporophyte ; A shows the apical cell {x\ X315 ; D, longitudinal section of a similar root, X960 ;
£, vascular bundle of the root, X 36a

least, by a single apical cell, which probably is to be traced back
directly to one of the original octants of the embryo. Whether
this is always the case in the youngest stages cannot be de-
termined until further investigations are made. Farmer^ was

* Fanner (3), p. 267.

IX MARATTIACE^^ISOETACEjE 265

unable to make out a single initial in AngiopteriSy which other-
wise agrees closely with Marattia,

The study of the root was confined mainly to the older
embryos, and although some variation is noticed, it is pretty
certain that there is a single apical cell, not unlike that found
in the Ophioglossaceae. Whether this can be traced back to
one of the primary hypobasal octants, it is impossible now to
say ; but Farmer's ^ statement that in Angiopteris there is at
first a three-sided apical cell would point to this. Unfortunately
my own preparations of Marattia were too incomplete to
decide this point in the latter. In the older root the form of
the apical cell was usually a four-sided prism, from all of
whose faces segments were cut off, although sometimes an
approach to the triangular form found in the Ophioglossaceae
was observed.

The foot is much less prominent than in Botrychium, and
in this respect the Marattiaceae are more like Ophioglossum?
In Marattia all the superficial cells of the central region of the
embryo become enlarged and act as absorbent cells for the
nourishment of the growing embryo.

As the embryo grows, the surrounding prothallial tissue
divides rapidly, and a massive calyptra is formed which com-
pletely encloses the young sporophyte for a long time. Owing
to the position of the cotyledon and stem, which grow up
vertically through the prothallium, a conspicuous elevation is
formed upon its upper side, through which the cotyledon finally
breaks. A similar elevation is formed by the calyptra upon
the lower side, through which the root finally penetrates, but not
until after the cotyledon has nearly reached its full development.
The prothallium does not die immediately after the young
sporophyte becomes independent, but may remain alive for
several months afterwards, much as in Botrychium.

The first tracheary tissue arises at the junction of the bundles
of the cotyledon, stem, and root. These primary tracheids are
short and their walls are marked with reticulate thickenings.
From this point the development of the tracheary tissue, as
well as the other elements of the bundles, proceeds toward the
apices of the young organs. The formation of the secondary
tracheids is always centripetal.

Short hairs with cells rich in tannin, and staining strongly
1 Farmer (3), p. 268. * Mcttenius (2), PL XXX.

266

MOSSES AND FERNS

CHAP.

with Bismarck-brown, occur sparingly upon the leaves and stem
of the young sporophyte.

The fully-developed cotyledon has the fan-shaped lamina
somewhat lobed, and the two primary veins arising from the
forking of the original vascular bundle usually fork once more,
so that the venation is strictly dichotomous in character.
Farmer ^ figures the cotyledon of Angiopteris as more spatulate
in form, with a distinct midrib, but this is never the case in
M. Douglasii, The nearly cylindrical petiole is deeply
channeled upon the inner side, and the single axial vascular
bundle is almost circular in section. While the crescent-shaped
mass of tracheary tissue is completely surrounded by the

phloem, the latter \s
much more strongly
developed upon the
outer side, and the
bundle approaches
the collateral form of
Ophioglossum, In-
deed, if the tannin
cells, which are found
here, belong to the
cortex, as Farmer
asserts to be the case
in Angiopteris^ the
bundle would be truly
collateral, as these are
immediately in contact with the tracheids. The lamina of the
cotyledon is similar in structure to that of the later leaves, and
differs mainly in the smaller development of the mesophyll.
The smaller veins have the xylem reduced to a few (1-3) rows
of tracheids upon the upper side of the collateral bundle.
Stomata of the ordinary form occur upon the lower side of the
leaf.

As the root finally breaks through the calyptra and pene-
trates into the earth, numerous fine unicellular root -hairs
develop from the older parts, but the tip for some distance
remains free from them. Owing to the numerous irregularities
in the cell divisions, the exact relation of the tissues of the
older parts of the root to the segments of the apical cell is

^ Farmer (3), Figs. 19-21.

Fig. 138. — Horizontal section of the lamina of the cotyledon of
M. DoHglasii^ X260.

MARA TTIACE2E—ISOETACE2E

267

,--i

.-•-F.

impossible to determine, and evidently is not always exactly
the same. The root -cap is derived mainly from the outer
segments of the apical cell, but also to some extent from the
outer cells of the lateral segments ; and the plerome cylinder,
where the base of the apical cell is truncate, is formed mainly
from the basal segments,
but in part as well from
the inner cells of the
lateral segments.

The vascular cylinder
of the root is usually
tetrarch. At four points
near the periphery small
spiral or annular tracheids
appear, and from them the
formation of the larger
secondary tracheids pro-
ceeds toward the centre.
The phloem is made up
of nearly uniform cells
with moderately thick
colourless walls. A bundle-
sheath is not clearly to be
made out (Fig. 137).

The cotyledon is des-
titute of the stipules found
in the perfect leaves of the
Marattiaceae, but they are
well developed in the third
leaf, where they form two
conspicuous appendages
clasping the base of the
next youngest leaf. The
edges of these stipules are
somewhat serrate, and the
edges of the two meet,
much like two bivalve shells. The strictly dichotomous
character of the cotyledon is gradually replaced in the later
leaves by the pinnate arrangement, both of the divisions of the
leaf and the venation. This is brought about in both cases by
an unequal dichotomy, by which one branch develops more

Fig. i3g.^Jlfarattia Doug^lasii (Baker). A, Longitudinal
section of the young sporophyte, showing the distri-
bution of the vascular bundles, X 6 ; /, leaves ; si,
stem apex ; r, a root ; y; the foot ; B, young sporo-
phyte with the prothallium (^X still persisting.

268

MOSSES AND FERNS

CHAP.

Strongly than the other, so that the latter appears lateral.
With the assumption of the pinnate form the leaf also develops
the wings or appendages upon the axis between the pinnae.
In the fully-developed leaves of the mature sporophyte, the last
trace of this is seen in the ultimate branching of the veins,
which is always dichotomous.

The second root arises close to the base of the second leaf,
and at first there seems to be one root formed at the base of
each of the young leaves ; in the older sporophyte the roots are
more numerous. Holle^ states that this is not the case in
Marattiay where only one root is formed for each leaf, in
Angiopteris two. This, however, requires confirmation in the
older plants. As the roots become larger it is no longer

Fig. 140. — A, Longitudinal section ; 6, transverse section of roots from older sporophyte of
M. DoHglasil, showing apparently more than one initial cell, x aoo.

possible to distinguish certainly a single initial cell. The
adjacent segments themselves assume to some extent the
function of initials, and thus in place of the single definite
apical cell a group of apparently similar initials is formed, which
takes its place (Fig. 140). This seems to be in some d^^ree
associated with the increase in size of the roots.^

According to Holle ^ the four-sided apical cell found in the
stem of the young sporophyte is retained permanently, but in
Angiopteris this is not the case, as in the older sporophyte a
single apical cell is not certainly to be made out Bower*

1 Holle (2), p. 217.

* It is possible that a single initial may be present even here, but the great similarity
of the central group of cells makes this exceedingly difficult to determine.
' Holle, Ic, p. 218. ♦ Bower (11), p. 324.

MARA TTIACE^E—ISOETACE^

269

comes to the same conclusion as Holle, although in an earlier
paper ^ he attributes a single apical cell to the stem of Angi-
opteris. The stem in both genera becomes very massive, but
its surface is completely covered by the persistent stipules.
The arrangement of the bundles is like that of Ophioglossum^
and they form a hollow cylinder with distinct meshes corre-
sponding to the position of the leaves. The bundles are,

Fig. 141. — MarcUtia Douglatii (Baker). A, Cross-section of the ultimate racbis of a fully-developed
leaf, X 96 ; B, part of the vascular bundle of the same, X aoo ; C, collenchyma from the cortex
of the same, x 150 ; D, cross-section of the lamina of the cotyledon, X 200 ; jcy^ xylem.

according to Holle,^ concentric, but the phloem more strongly
developed upon the outer side.

The thick petioles of the full-grown leaves are traversed by
very numerous vascular bundles, which at the base give off
branches that supply the thick stipules within which they
branch and anastomose to form a network. These bundles in
Angiopteris are arranged in several circles, or according to
De Vriese and Harting,^ the central ones form a spiral. In
the rachis of the last divisions of the leaves, however, both of

Bower (2), p. 579.

« Holle (2), p. 217.

' De Vriese (i).

270

MOSSES AND FERNS

Marattia and AngiopteriSy there is but a single axial bundle, as
in the petiole of the cotyledon.

Fig. 142, B shows a cross-section of a pinnule from a large

IX MARATTIACEjE^ISOETACE^ 271

leaf of A, evectUy which has much the same structure as that of
Marattia, The central vascular bundle is horse -shoe shaped
in section, and shows a central mass of large tracheids with
reticulate or scalariform markings, surrounded by the phloem
made up of very large sieve-tubes much like those of Botrychium^
and with these are the ordinary protophloem cells and bast
parenchyma. A distinct bundle-sheath is absent, as, according
to Holle,^ it is from all the bundles in both Marattia and
AngiopteriSy except those of the larger roots. The bulk of the
ground tissue is composed of large parenchyma cells, but on
both sides just below the epidermis is a band of colourless cells
which resemble exactly the coUenchyma of Phanerogams. In
the base of the petiole this becomes harder and forms a colour-
less sclerenchyma, according to Holle,^ which in Danaa is
replaced by brown sclerenchyma like that of the true Ferns.
In the lamina of the leaf in Angiopteris too, the arrangement
of the tissues is strikingly like that of the typical Angiosperms.
A highly-developed palisade parenchyma occupies the upper
part of the leaf beneath the epidermis, which bears stomata only
on the lower side of the leaf. The rest of the mesophyll is
composed of the spongy green parenchyma found in the other
Ferns. The smaller veins both here and in Marattia have
collateral bundles.

TIte Sporangia

The sporangia of the Marattiaceae differ most markedly
from the Ophioglossaceae in being borne on the lower side of
the ordinary leaves, and not on special segments. Except in
Angiopteris, they form synangia, whose development has only
been studied in Marattia? Luerssen describes the process
thus : " In Marattia the first differentiation of the sporangium
begins while the young leaf is still rolled up between the
stipules of the next older one. The tissue above the fertile
vein is more strongly developed than the adjoining parenchyma,
and forms an elevated cushion parallel with the vein. This is
the receptacle, which develops two parallel ridges, separated by
a cleft. These two ridges grow up until they meet, and their
edges grow together and Completely close the cleft which lies
between. In each half there are differentiated the separate

* Holle (2), p. 216. ^ Holle (2), ibid, ' Luerssen (7), vol L p. 579.

272

MOSSES AND FERNS

CHAP.

archesporial groups of cells corresponding to the separate
chambers found in the complete synangium." The whole
process takes, according to his account, about six months.
Luerssen was unable either in Marattia or Angiopterts to trace
back the archesporium to a single cell, which Goebel ^ claims is
present in the latter.

In Angiopterts the process begins as in Marattia^ but at a
period when the leaf is almost completely developed and
unfolded. The first indication of the young sorus is the

Fig. 143. — A ngiopteris evecta (Hoffm). Development of the sporangium. A, Vertical section of wy
young receptacle ; B, similar section of an older sporangium in which the arche^x>rium is already
developed (after Goebel) ; C, longitudinal section of an almost fully-developed sporangium, sboviaf
the persistent tapetal cells (/); r, the annulus, X75.

formation of an oblong depression above a young vein, and
about the border of this are numerous short hairs, which as a
rule are absent from the epidermis of the leaf (Fig. 143, A).
The placenta is formed as in Marattia^ but instead of the two
parallel ridges that are found in the latter, the young sporangia
arise separately, much as in Botrychium. As in the latter too,
Goebel states that the archesporium can be traced to a single
hypodermal cell in the axis of the young sporangium. This

1 Goebel (3).

IX MARA TTIA CE^—ISOETA CE^ 273

cell divides repeatedly, but apparently without any definite
order, and the division of the spores follows in the usual way.
From the cells about the archesporium tapetal cells are cut off,
but these do not disappear, as Goebel ^ asserts, but persist until the
sporangium is mature. The growth is greater upon the outer
side, which is strongly convex, while the inner face is nearly flat.
A section of the nearly full-grown sporangium (Fig. 143, C)
shows that the wall upon the outer side is much thicker,
and is composed for the most part of three layers of cells,
of which the outer in the ripe sporangium have their outer
walls strongly thickened. The top of the sporangium and the
inner wall are composed of but one layer of cells (exclusive of
the tapetum), which are flat and more delicate than those upon
the outer side. Near the top on its outer side is a transverse
line of cells with thickened darker walls, which project some-
what above the level of the others. This is the annulus or
ring, and resembles closely that of Osmunda, Lining the wall
is a layer of very large thin-walled cells which form the tapetum.
This in Angiopteris remains intact until the spores are divided.
Whether it disappears before the dehiscence of the sporangium
was not determined. The contents of these cells, which are
very much distended, and evidently actively concerned in the
growth of the forming spores, contain very few granules, but
are multinucleate in many cases. Whether this condition is
due to a coalescence of originally separate cells, or what seems
more likely, arises simply from nuclear division in the young
tapetal cells, without the formation of cell walls, was not
decided. The young spore tetrads, at this time, are embedded
in an apparently structureless mucilaginous matter, which stains
uniformly with Bismarck-brown. This apparently is secreted
by the tapetal cells for the nourishment of the spores.

Classification of Marattiacece

The living forms are divisible into three families : —

I. Angiopterideae, with the single genus Angiopteris, and
probably only one extremely variable species, A. evecta (Hoffm),
which occurs throughout the Eastern tropics.

II. Marattieae, with two genera, Marattia and Kaulfussia?

1 Goebel (3), 1881, p. 684.

* Kaulfussia is sometimes made the type of a separate family.

274 MOSSES AND FERNS chap.

The former genus includes seven species^ belonging to the
tropics of both the old and new world. The latter includes but
a single species, belonging to south-eastern Asia. The synangia
are scattered over the lower surface of the palmate leaf, and are
circular, with a central space into which the separate loculi open
by a slit, as in Marattia, Kaulfussia is characterised by very
large pores upon the lower side of the leaf. A study of the
development of these shows* that at first they are perfectly
normal in form, and that the large round opening is a secondary
formation, the two guard cells of the young stoma being toni
apart, and disappearing almost entirely in the older leaf.

III. The Danaeaceae. The single genus Daruea includes
eleven species, according to Hooker,^ all confined to the new
world. They are Ferns of moderate size, with simple or pin-
nate leaves, whose venation is like that of Angiopteris, The
synangia are long, and frequently extend completely from the
midrib to the margin of the leaf. They are like those of
Marattia, but open by a terminal pore instead of by a slit
Between the synangia the tissue of the leaf in some species
forms an elevated ridge, with the top broader, so that the section
is T-shaped.

Fossil MarattiacecB

It has been shown * that the majority of the earlier fossil
Ferns belong to this order, and of the living families the
Angiopterideae and Danaeacese have also representatives in a
fossil condition. The Marattieae and Kaulfussieae are only
known in a living state. Five families, on the other hand,
contain only fossil forms, some of which appear to be in certain
respects intermediate between the Marattiaceae and some of the
leptosporangiate Ferns.^

The Isoetacece

The systematic position of this extremely isolated group
has been long a debated .question. Most botanists assign it a
place near the Lycopodineae, but there are serious objections to
this, and it seems to the writer that at present the weight of
evidence is in favour of placing Isoetes with the eusporangiate

1 Hooker (i). » i.uerssen (i). ^ Hooker (i).

* Solnis-Laubach [z\ p. 143. » Solms-Laubach, Lc. p. 148.

MARA TTIACEjE—ISOETACE^

275

Filicineae, although it must be understood that this is
provisional.

Fig. 144.— a, Plant of IsotUs Boianderi (Englm), x i ; B, base of a leaf with nuicrosporangium, X 4 ;

/, ligula ; c, velum.

Isoetes has been the subject of repeated investigation,
Hofmeister ^ being the first to study its development in detail.

^ Hofnieister (i).

276 MOSSES AND FERNS chaf.

The sporophyte is in most species either aquatic or amphibious,
but a few species are terrestrial. They are very much alike in
appearance, having a very short stem whose upper part is
completely covered with the overlapping broad bases of the
leaves, which themselves are long and rush-like, so that the'
plant in general appearance might be readily taken for an
aquatic Monocotyledon. The roots are numerous and
dichotomously branched. The stem grows slowly in diameter,
and the older ones show two or three vertical furrows that unite
below, and as the stem continues to grow these furrows deepen,
so that the old stem is strongly two or three lobed. In the
furrows the roots are formed in acropetal succession. The
leaves are closely set and expanded at the base (Fig. 144) into
a broad sheath, with membranaceous edges. Just above the
base of each perfectly -developed leaf is a single very lai^
sporangium, sunk more or less completely in a cavity (fovea),
which , in most species is covered wholly or in part by a
membranaceous indusium (velum), and above the fovea is a
scale-like outgrowth of the leaf, the ligula. The spores are of
two kinds, borne in separate sporangia. ^Die^-^>^«r leaves of
i each cycle produce microspores^ the i»aSrones macrospores,
• many times larger than the former. The innermost leaves,
which are not usually perfectly developed, are sterile, and
separate one year's growth from the next. In some of the
land forms, e,g, /. hystrix^ these sterile leaves are very much
reduced, and form spine-like structures.

Tfie Gametophyte

The germination of the microspores was studied ' by
Hofmeister,^ and later by Millardet* and Belajeff,* the later
writer differing in some essential particulars from the earlier
observers. The two former studied /. lacustris^ and Belajeff
/. setacea and /. Malitwerniana^ which do not seem to differ,
however, from /. echinospora, which was investigated by the
writer. The microspores of all the species are bilateral, and are
small bean-shaped cells with thick but in most species nearly
colourless walls. The epispore sometimes has spines upon it,
but in /. echinospora var, Braunii the surface of the spore is
nearly smooth. In this species the faiT^ begin to ripen in the

* Hofmeister (i), p. 341.

^ Millard^

Ti).

^» Belajeff (I),

MAI^A TTIA CE^—ISOETA CE^

277

early autumn, and continue to do so as long as the conditions
permit- of growth. The spores are set free by the decay of the
sporangium wall, which probably in nature is not completely
the case until winter or early spring, which seems to be the
natural time for germination. If they are set free artificially,
however, they will germinate promptly, especially if this is done
late in the autumn or during the winter. Thus spores sown in
December produced free spermatozoids in two weeks. The
spores do not all germinate with equal promptness, and all

Fic;. 145.— A, Young male prothallium of Isottes utacta (A. Br.) ; r, vegetative cell, X 1280 ; B, two
fully-developed male prothallia of /. echinos^ora var, Braunii (Durieu), X xaoo ; I, horizontal
section; II, vertical section; C, spermatozoid o( I. Maiinvtrmana, XZ480. A and C after
Belajeff.

stages of development may be met with in the same lot. The
ripe spore has no chlorophyll, but contains besides the nucleus,
albuminous granules, small starch grains, and oil.

The first division wall cuts off a small cell from one end,
which undergoes no further development, and represents the
vegetative part of the prothallium, which is here absolutely
rudimentary. The rest of the spore forms at once the single
antheridium. In the latter two, walls are formed so inclined to
each other as to include two upper cells and one lower one
(Fig. 145). This latter next divides into two by a vertical

278 MOSSES AND FERNS chap.

longitudinal wall, and each of the resulting cells is further
divided by a periclinal wall, so that the antheridium consists of
four peripheral cells and two central ones. The latter finally
divide again, by vertical walls, making four central cells, which
become at once the sperm cells. According to Belajeff ^ the
walls of the peripheral cells become dissolved finally, so that the
sperm cells float free within the spore cavity. Each sperm cell
forms a single coiled spermatozoid, which is more slender than
those of Marattiay but like them is multiciliate.

The macrospores are very many times larger than the
microspores, and are of the tetrahedral type instead of bilateral.
They are nearly globular in form and show plainly the three
converging ridges on the ventral surface. If the fresh spore is
crushed in water, its contents appear milky, and microscopic
examination reveals numerous oil -drops and some starch-
granules, mingled with roundish bodies of albuminous nature
The latter absorb water and swell up so that fhey look like firee
cells.

The wall of the spore is very thick. The perinium is thick
and transparent in appearance, and in the species under
consideration provided with short recurved spinules. The
interior, in microtome sections, is filled with coarsely granular
cytoplasm, which often appears spongy, owing no doubt to the
dissolving out of the oil. Scattered through the cytoplasm are .
round starch-granules with a central hilum. The large nucleus
lies in the basal part of the spore.^ It is broadly oval in outline,
and the cytoplasm immediately about it is nearly free from
large granules. Before germination begins there are few
chromosomes, and the nucleolus does not stain readily.

After the spores have lain a few days in water, the nucleus
increases in size, and then the nucleolus stains very intensely
and the chromosomes become more conspicuous. The nucleus
divides while still in its original position, and undergoes division
in the usual way. A very evident cell plate is formed in the
equator of the nuclear figure (Fig. 146, A), but no cell wall is
found, and the result of the division is two large free nuclei.
The next youngest stage observed (Fig. 146, B) had four free
nuclei, which now had moved to the ventral side of the spore.

1 Belajeff (I), p. 797.

* Fanner {Anna/s of Botany^ December 1890) states that in /. lacustris the
nucleus lies near the apex of the spore.

MARA TTIACE^—ISOETACE^

279

These are very much smaller than the primary one, but are
relatively richer in chromatin. They continue to divide until
there are from about thirty to fifty free nuclei, but as yet no
trace of cell division can be seen. Most of the nuclei lie in

the ventral part of the spore, close to the outer wall, but an
occasional one may be detected elsewhere.

Cell division begins at the apex (ventral part) of the spore.
At this time the cytoplasm stains more deeply than before,
and sometimes e^^tremely delicate threads may be detected.

28o MOSSES AND FERNS cha?.

radiating from the nuclei and connecting adjacent ones (Fig.
146, C). The first traces of the division walls appear simul-
taneously between the nuclei in the form of cell plates composed
of minute granules, probably of cellulose, which quickly coalesce
and form a continuous membrane. In this way the upper
part of the spore becomes transformed into a solid tissue (Fig.

147).

The cell formation proceeds quickly toward the base of the
spore, following the spore wall, so that for a time the central
space remains undivided. The whole process recalls most
vividly the endospore formation of most Angiosperms. On
account of the extremely thin walls and dense contents of the
young prothallial cells it is not easy to determine exactly when
the whole spore cavity becomes filled up with cellular tissue.
Because of the greater number of free nuclei in the upper part
of the spore, and their consequent close proximity, the cells
are smaller than those in the central and basal parts of the
prothallium. Sometimes the transition from this small-celled
tissue to the large-celled tissue of the basal part is quite abrupt,
and the more noticeable as the upper cells are more trans-
parent ; but there was nothing to indicate that this was in any
way connected with the early divisions of the primary nucleus,
and more often no such sudden transition was seen.

Hofmeister's account of the coalescence of previously
separate cells to form the prothallium was obviously based
upon incorrect observation, and is not borne out by a study of
sections of the germinating spore.

The first archegonium is very early evident, generally
before the cell division is complete in the lower part of the
spore. It occupies the apex of the prothallium, and the
mother cell is distinguished by its large size and dense granular
contents. It is simply one of the first-formed cells that soon
ceases to divide, and as its neighbours divide rapidly the
contrast between them becomes very marked. Whether seen
from above or in longitudinal section, it generally is triangular,
or nearly so. In the structure of the mature archegonium,
OphioglossufHy to judge from Mattenius* somewhat incomplete
account, shows strong points of resemblance, as do the
Marattiaceae.

The development of the archegonium corresponds almost
exactly with that of Marattia, but the basal cell is always

MARA TTIACE^—ISOETACE^

281

wanting, and the first transverse wall separates the central cell
from the cover cell. The first division in the inner cell is

Fig. S47. — Itottts tchhuu/ora var. Braunii (Dur.). A, Longitudinal section through the apex of
the female prothalllum, showing the first cell formation, X 300 ; B, similar section of a prothallium
with the divisions completed and the first archegonium ijir) already opened.

parallel with the base of the cover cell, and divides it into the
primary canal cell and central cell. The contents of the three

282

MOSSES AND FERNS

cells of which the archegonium is now composed are similar,
and the nuclei large and distinct. The cover cell next divides
into four by transverse walls (Fig. 146, E), and from these, as in
Marattia^ the four rows of cells of the neck are formed. The
number in each row is four in the mature archegonium. The
ventral canal cell, which like that of Marattia extends the
whole breadth of the central cell, is separated almost simul-

Fio. 148.— Isoetet ecktMospora var. Braunii (Dur.). Development of the archegonium, x 500 ; «. tbc
«gg ; v% ventral canal cell ; A, neck canal cell ; D shows a two-celled embryo within the arche-
gonium.

taneously with the appearance of the first transverse divisions
in the neck cells. The neck canal cell has at first a single
nucleus, which later divides, but there is no division wall
formed. Although the number of cells in each row of the
neck is usually greater than in Marattia^ the neck canal cell
is shorter and extends but little between the neck cells (Fig.
148, B).

The egg is very large, round or oval in form, and the

IX MARATTIACE^—ISOETACE^ 283

nucleus contains a large round body (nucleolus?) that stains
very intensely, but otherwise shows little chromatin. The
receptive spot is of unusual size, and occupies about one-third
of the egg. It is almost hyaline, showing, however, a faint
reticulate arrangement of fine granules ; the lower portion of
the egg is filled with granules that stain strongly.

In /. lacustriSy according to Hofmeister,^ only one arche-
gonium is formed at first, and if this is fertilised, no others are
produced ; but in /. eckinospora^ even before the first archegonium
is complete, two others begin to develop and reach maturity
shortly after the first, whether the latter is fertilised or not.
In case all of these primary archegonia prove abortive, a small
number, apparently not more than five or six, may be formed
subsequently ; but so far as my observations go, the production
of archegonia is limited, as is the growth of the prothallium
itself.2

The development of the prothallium goes on without any
increase in size, until the first archegonium is nearly complete,
about which time the spore opens along the line of the three
ventral ridges, and the upper part of the enclosed prothallium
is exposed, but projects but little beyond the opening. In
case all the archegonia prove abortive, the prothallium con-
tinues to grow until the reserve food material is used up, but
then dies, as no chlorophyll is developed in its cells, and only
in very rare instances are root-hairs formed.

The Embryo

Besides the earlier account of Hofmeister,^ Kienitz-Gerloff *
and Farmer ^ have made some investigations upon the embryo-
geny of /. lacustriSy which correspond closely, so far as they go,
with my own on /. echinospora.

The youngest embryos seen had the first division wall
complete (Fig. 148, D). This is transverse, but more or less
inclined to the axis of the archegonium. The nuclei of the
two cells are large and contain several chromatin masses. The
second division in the epibasal and hypobasal cells does not

^ Hofmeister (i), p. 340.

* Kienitz-Gerloff (6) states that in old prothallia of /. lacustris the number is
sometimes twenty to thirty.

' Hofmeister (i). * Kienitz-Gerloff (6). » Farmer (2).

284 MOSSES AND FERNS chap.

always occur simultaneously, the lower half sometimes dividing
before the upper one, and at times the second walls are at
right angles instead of in the same plane. Of the quadrants
thus formed, the two lower form the foot, and the two upper
ones the cotyledon and primary root. The stem apex arises
secondarily at a later period, and probably belongs to the
same quadrant as the root ; but as it does not project at all,
and is not certainly recognisable until after the boundaries
between the quadrants are no longer evident, this cannot be
positively asserted.

Sometimes the quadrants divide into nearly equal octants,
but in several young embryos examined, no definite octant
walls were present, at least in the upper octants, but whether
this is a common occurrence would be difficult to say. The
next divisions in the embryo resemble those in Marattia, and
as in the latter it may be said that the young members of the
embryo grow for a short time from an apical cell, inasmuch as
the tetrahedral octants at first have 3egments cut off parallel
with the basal, quadrant, and octant walls, leaving an outer
cell (Fig. 149, A) that still retains its original form ; but very
soon periclinal walls arise in this cell in each quadrant, and it
is no longer recognisable as an apical cell, and from this time
the apex of the young member grows from a gfroup of initial
cells.

Up to this time the embryo has increased but little in size,
and retains the globular or oval form of the egg. It now
elongates in the direction of the basal wall, and soon after the
cotyledon and primary root become differentiated. The axis
of the former coincides with the plane of the basal wall, and it
approaches more or less the vertical as the latter is more or
less inclined. Occasionally the basal wall is so nearly vertical
that the cotyledon grows upright and penetrates the neck of
the archegonium at right angles to its ordinary position. At
the base of the leaf at this stage a single cell, larger than its
neighbours, may often be seen (Fig. 150, /). This is the
mother cell of the ligule, found in all the leaves. This cell
projects, and as the leaf grows divides regularly by walls in a
manner compared by Hofmeister to the divisions in the
gemmae of Marchantia, It finally forms a scale-like appendage
about twelve cells in length by as many in breadth.

Almost coincident with the first appearance of the ligule

MARA TTIA CE^—ISOETA CEjE

285

a depression is evident, which separates the bases of the
cotyledon and root. The base of the latter, which begins
now also to grow in length, projects in the form of a semi-
circular ridge that grows rapidly and forms a sheath about the
ligule and the base of the cotyledon (Fig. 152, v). The growth
of this sheath is marginal, and continues until a deep cleft is
formed. A number of cells at the bottom of the latter between
the sheath and the leaf base constitute the stem apex. As

Fig. 149. — A, An embryo of /. tchinosp^ra var. Braunii, with unusually regular divisions, X450;
B, a much older one, still enclosed within the prothallium, X 150 ; ar, archegonia.

they differ in appearance in no wise from the neighbouring
cells, it is quite impossible to say just how many of them
properly belong to the stem. So far as can be judged, the
origin of the growing point of the stem is strictly secondary,
and almost exactly like that of many Monocotyledons.^

Longitudinal sections of the embryo, when root and leaf
are first clearly recognisable, show that the foot is not clearly
defined, as the basal wall early becomes indistinguishable from
the displacement due to rapid cell division in the axis of the

* See Hanstein's figures of Alistna, for example, in Goebers Outlines, Fig. 332.

286

MOSSES AND FERNS

embryo. It projects but little, and the cells are not noticeably
larger than those of the cotyledon and root.

As the cotyledon lengthens it becomes somewhat flattened,
and in the later stages its increase in. length is due entirely to
basal growth. Even in very young embryos a distinct
epidermis is evident in the leaf, and about the time that the
ligule is formed the first trace of the vascular tissue appears.

Fig. 150. — Development of the embryo in /. tchtHOspora var, Braunii (Dur.X A, Median longi-
tudinal section of a young embryo ; B, four horizontal sections of a younger one ; C, two vertical
transverse sections of an older embr>'o ; /, the ligula, x 300.

This consists of a bundle of narrow procambium cells, which
lie so near the centre of the embryo that it is impossible to
assign it certainly to either root or leaf; indeed it sometimes
seems to belong to one quadrant, sometimes to the other.
From it the development of the axial bundles of cotyledon and
root proceeds, and by it they are directly united. The section
of the plerome cylinder of the leaf is somewhat elliptical, and

MARA TTIA CEjE—ISOETA CEJ£

287

it does not extend entirely to the end. Its limits are clearly
defined from the periblem, in which the divisions are mainly
transverse and the cells arranged in regular rows.

The primary xylem consists of small sjSiral and annular
tracheids at the base of the leaf, and from these the formation
of similar ones proceeds towards the tip. Their number is
small, even in the full-grown leaf, and they are the only

Fig. 151.— Three successive horizontal sections of a somewhat advanced embryo of /. echinos^ora
var, Braunilt X 260 ; R, root ; cot^ cotyledon ; f /, stem ; /, ligula.

differentiated elements, the rest of the bundle showing only
elongated parenchyma, much like the original procambium
cells.

The axis of growth of the primary root usually coincides
with that of the cotyledon, but this is not always the case. In
the very young root (Fig. 152, R) the end is covered with a
layer of cells continuous with the epidermis of the rest of the

288 MOSSES AND FERNS chap.

embryo. Beneath are two layers of cells concentric with the
epidermis. From the inner one arises the initial cell (or cells ?)
of the plerome, which soon becomes well defined and connected
with the primary strand of procambium in the axis of the
embryo. It is quite possible that here, as in the older roots,
a single initial cell is present in the plerome, but this is not
certain. The layer of cells immediately below the primary
epidermis is the initial meristem for all the tissues of the root
except the plerome. The primary epidermis later divides into
two concentric layers which take no further part in the growth
of the root except as they join the outer layers of the root-cap.
From the layer above the plerome initial, additions are

Fig. 152. — Median longitudinal section of an embryo of the same species shortly before tlie cocyledoo
breaks through the prothallium ; lettering as in the preceding, X 300.

made at regular intervals to the root -cap, and these layers
remain one cell thick, so that the stratification is very marked.
At the apex of the root there is no separation of dermatogen
and periblem, which are first differentiated back of the apex.
The primary xylem consists of very delicate spiral tracheids
formed at the base of the root at the same time that the first
ones appear in the leaf.

The foot increases much in size as the leaf and root develop,
and its superficial cells become much enlarged and encroach
upon the large cells of the prothallium, whose contents are
gradually absorbed by it.

The cotyledon is at first composed of compact tissue, which

MARA TTJACE^-ISOETACEjE

289

during its rapid elongation separates in places, and forms a
system of large intercellular spaces. There are two rows of
very large ones, forming two broad air-chambers extending the
whole length of the leaf, but which are interrupted at intervals

Fig. 153.— a. Median section of a young sporophyte writh the second leaf L^ already formed ; r««,
second root ; sty stem«apex, X 150; B, cross-section near the base of the cotyledon, showing the
intercellular spaces / and the second leaf V? surrounded by the sheath v at the base of the coty-
ledon ; /, the ligule of the cotyledon, x 300.

by imperfect partitions composed of single layers of cells. In
the root there are similar lacunae, but they are smaller and
less r^ularly arranged.

290

MOSSES AND FERNS

The growing embryo is for a long time covered by the
prothallial tissue, which in the upper part continues to grow
with it ; but finally cotyledon and root break through, the
former growing upward, the root bending down and anchoring
the young sporophyte in the mud. Owing to the large air-
spaces the cotyledon is lighter than the water, and always
stands vertically, whether the original position was vertical or
horizontal. In the latter case the plant appears to be attached
laterally to the prothallium, and the stem apex, which when
first formed stands almost vertically, now assumes the horizontal
position which it has in the older sporophyte.

About the time that the
young sporophyte breaks
through the prothallium, the
second leaf begins to develop.
The growing point (Fig. I 5 3, st)
now lies in the groove bet\*'een
the base of the root and the
cotyledon, and its nearly flat
surface is at right angles to the
axis of the latter. The second
leaf (L^) arises as a slight eleva-
tion on the side of the stem
directly opposite the cotyledon.
From the first it is multicellular,
and its growth is entirely like
that of the cotyledon, which
it otherwise resembles in all re-
spects. Almost as soon as the
leaf is evident at all, a strand of procambium cells is formed
running from the junction of the cotyledon and first root, and
is continued into the second leaf as its plerome.

The second root develops from the base of the second leaf
in the immediate vicinity of the common fibrovascular bundle,
and is formed about the time that the leaf begins to elongate.
A group of cells here begins to multiply actively, and very
soon shows a division into the initials of the tissue systems of
the young root. From this time the growth proceeds as in
the primary root, and it finally breaks through the overlying
tissues.

The stem has no vascular bundle apart from the common

Fig. 154. — Longitudinal section of the second
root, X 535 ; //, plerome.

IX MARATTIACEjE—ISOETACE^ 291

bundle formed from the coalescence of the bases of the bundles
from the leaves and roots. In all the later-formed leaves and
roots there is but a single axial bundle. In the leaves this is
decidedly collateral in form with the poorly -developed xylem
upon the inner (upper) side. Except for their larger size, and
their having usually four instead of two air-channels, the later
leaves resemble in all respects those first formed.

The development of the young plant was not followed
beyond the appearance of the third leaf, but it probably in its
later history corresponds to 7. lacustris. Here, according to
yHofmeister,^ the opposite arrangement of the leaves continues
up to about the eighth, when the \ divergence is replaced
successively by \, f , f , -^^^ and ^, which is the condition in
the fully-developed sporophyte.

The Sporophyte

The structure of the mature sporophyte has been the
subject of repeated investigations, the most recent being those
of Farmer,^ who has made a most careful examination of the
vegetative organs. The thick, very short stem has a central
vascular bundle, which as in the young plant is made up of the
united leaf-traces, and there is no strictly cauline portion, as
Hegelmaier ^ and Bruchman * assert. This central cylinder is
composed of very short tracheids, with spiral and reticulate
markings, mixed with similarly -shaped cells with thin walls.
Surrounding this xylem-cylinder is a layer of cells, which
Farmer calls the " prismatic layer." This, according to Rus-
sow,^ is continuous with the phloem of the leaf- traces, and
he regards it as the phloem of the stem bundle. Outside of ^
this prismatic layer is a zone of meristematic cells, which for
the " cambium." The cells of this zone are like those ot^he
cambium of Botrychium or of the Spermaphytes, and like these
new cells are formed on both sides ; but those fopried upon
the outside remain parenchymatous and are gj^kdlJally thrown
off with the dead outer cortex, but those upon the inner
side develop into the prismatic cells, mingled with which are
cells very like the tracheids, except that they retain to some

' Hofmeister (i), p. 354. "^ Farmer (2).

^ Hegelmaier (i). "* Bruchman (1).

* Russow (i), p. 139.

292 MOSSES AND FERNS chap.

extent their protoplasmic contents. These cells are arranged
in more or less well-marked zones, and possibly mark the
limits of each year's growth. It will be seen from what has
been stated that while a true secondary thickening of the stem
occurs in Isoetes, it is quite different from that in Botrychium^
which closely resembles the normal thickening of the coniferous
or dicotyledonous stem. It has been compared to that found
in Yucca or Dracana, and this perhaps is more nearly like it
However, as the development of cambium and secondar>'
thickening have evidently occuri'ed independently in very widely
separated groups of plants, it is quite likely that we have here
one more instance quite unconnected with the same phenomenon
elsewhere.

The leaves, as already stated, differ but little from those of
the young plant. The vascular bundle is here somewhat better
developed, but remains very simple, with only a few rows of
tracheids fully developed. The phloem remains undifferentiated,
and no perfect sieve-tubes can be detected. The phloem lies
upon the outer side of the xylem, but shows a tendency to
extend round toward the upper side. Of the other Filicineae,
Ophtoglossutn comes the nearest to it in the structure of the
bundles. The air-channels are four in number in the fully-
developed leaf, and the diaphragms across them more regular
and complete. Instead of being throughout but one cell thick,
as in the first leaves, they are thicker at the edges, so that in
section they appear biconcave. In the older leaves the broad
sheath at the base is much better developed, and the over-
lapping leaf bases give the whole stem much the appearance of
the scaly bulb of many Monocotyledons. In all the terrestrial
species, and those that are but partially immersed, the leaves
are provided with numerous stomata of the ordinary form ;
but in some of the submersed species these are partially or
entirely wanting. The development of the ligule also varies,
being very much greater in the terrestrial species, where it
may possibly be an organ of protection for the younger
leaves.

Hofmeister^ states that in 7. lacustris the first sporangia

are not developed until the fourth year from the time the young

sporophyte is first formed. The sporophylls begin to form in

the third year, but it is a year more before the sporangia are

* Hofmeister (i), p. 364.

IX MARATTIACEjE—ISOETACEjE ^ 293

complete. From this time on, the regular succession of
sporophylls and sterile leaves continues.

There has been much disagreement as to the method of
growth in the root. The earlier observers attributed to it a single
apical cell, not essentially different from that of the true Ferns ;
this was shown to be incorrect by Bruchman ^ and Kienitz-
Gerloff,^ but Farmer ^ claims that none of these have correctly
described the structure of the larger roots, which differs
somewhat from that of the earlier ones. According to the
latter observer there is always a single initial for the plerome,
and above this two layers of meristem, one giving rise to the
inner cortex, the other to the outer cortex, as well as to the
epidermis and root-cap. The fibrovascular bundle is monarch,
like that of Ophioglossum vulgatum^ and the phloem becomes
differentiated before the xylem elements are evident.

The later roots arise much as the second one does in the
young plant, but the rudiment is more deeply seated. The
roots are arranged in 7. lacustris in four rows, two corresponding
to each furrow.* According to Bruchman * the first evidence of
a forming root is a single cell of the cortical tissue lying a
short distance outside of the leaf-trace. This, however, cannot
be looked upon as the apical cell, as it only gives rise to calyp-
trogen and dermatogen. The periblem and plerome arise from
the cells lying immediately below it.

The branching of the roots is a genuine dichotomy, and
has also been carefully studied by Bruchman. He states that
the process begins by a longitudinal division of the plerome
initial, and each of the new initials at once begins to form a
separate plerome. The overlying tissues are passive, and their
divisions are governed by the growth of the two plerome
strands.

The Sporangium

The development of the sporangium has been very carefully
examined by Goebel,* and his results confirmed by later
observers. All of the leaves, except the imperfect ones that
separate the sporophylls of successive years, bear a single, very
large sporangium at the base. From the first it consists of an

* Bruchman (i), p. 554. '^ Kienitz-Gerloflf (6).

' Farmer (2), p. 37. * Van Tieghem and Douliot (5).

* Bmchman (i), p. 558. « Goebel (3), Bot. Zeit, 1881.

294

MOSSES AND FERNS

CHAP.

elongated elevation composed of cells which have divided by
periclinal walls. In /. lacustris the sporangium arises mainly
from the three outer layers of cells thus formed. The lower
part of this cushion-shaped prominence forms the base or stalk,
while the archesporium is formed from the hypodermal layer of
cells (Fig. 15 s, A). Eiach cell of the archesporium shows an
independent growth, and up to this point the development of
macro- and micro-sporangia is the same. In the latter each

76--^

Fig. 155. — Isoeies lacustris (L.). A, Longitudinal section of young microsporangium ; B, similar
section of macrosporangium. The shaded cells in A, the nucleated ones in B, represent Uk
archesporium (after Goebel); C, transverse section of the sporophyll and microsporangiam,
X 8 ; /r, the trabecular (after Bower).

archesporial cell divides by a series of tangential walls and
at first all appear alike ; but soon some of the rows become
more transparent and divide less rapidly, so that they form
elongated tabular cells. The others divide in all directions
and form large masses of cells with abundant protoplasm.
These finally form the spore mother cells. The outer cells of
both sporogenous and sterile rows form the tapetum. The
sporangium at this stage consists of a series of irregular
chambers separated by incomplete layers of colourless cells

IX MARA TTIA CE^~ISOE TA CEjE 295

(trabeculae), and containing the spore mother cells (Fig. 1 5 5, C).
The whole process is not unlike that in the spike of Ophio-
glossum, especially if Bower's statement is correct that the whole
hypodermal layer in Ophioglossum is to be considered as the
archesporium.^

As the sporangium grows the tissue of the leaf surrounding
it grows up on all sides so as to enclose it in the fovea, whose
edges extend more or less over the sporangium to form the
velum. Goebel calls attention to the analogy of the latter with
the integument of an ovule.

The macrosporangium corresponds in its earlier stages
exactly to the microsporangium, and the difference between
them is first indicated by the fertile archesporial cells in the
former only dividing by the walls which form the tapetal cells,
and an inner cell of each row becomes at once the macrospore
mother cell. This is much larger than the others, and is very
conspicuous. Between the fertile rows are the trabeculae, at
first also only one row of cells. As the spore mother cell
grows, it encroaches upon, and destroys, the surrounding tapetal
cells, and lies in the cavity thus formed. The division into
four spores follows in the usual manner.

In the development of the sporangia, especially the forma-
tion of the large hypodermal archesporium, and perhaps also
the integument, the resemblance to corresponding structures in
the Spermaphytes is obvious, and in these respects Isoetes
certainly does come nearer the latter than any other living
Pteridophyte.

Bower * has recently made a careful study of the sporangium
of Lepidodendron and found structures which closely resembled
the trabeculae in that of Isoetes^ and is inclined to regard
this as an evidence of relationship between the two genera.

In /. lacustris the sporangium is sometimes replaced by a
leafy bud which may develop into a perfect plant.^

Ttie Affinities of ttie Eusporangiate Filicinece

In attempting to discover the affinities of the members of
this group, many difficulties are encountered. First, anjd
perhaps most important, is the small number of forms still

' Bower (14). * Bower (15).

^ Goebel, ** Ueber Sprossbildung aus Isoetesblatter," BoU Zeit, 1879.

296 MOSSES AND FERNS , chap.

existing, which probably are merely remnants of groups once
much more abundant. This is certainly true of the Maratti-
aceae, and presumably is the case with the Ophioglossaceae and
Isoetaceae as well. In the former order this is amply proven
by the geological record ; but in the others the fossil forms
allied to them are very uncertain, and as yet poorly understood.
In the Ophioglossaceae the series from Ophioglossum through the
simpler species of Botrychium to the higher ones, such as
B. Virginianum^ is complete and unmistakable, but when
points of connection between these and other forms are sought,
the matter is not so simple.

Our still very incomplete knowledge of the gametophyte
of the Ophioglossaceae makes the comparison doubly difficult.
From the development of chlorophyll in the germinating spore
of B, Virginianum^ as well as from analogy with other Ferns, it
seems probable at any rate that the subterranean chlorophylless
prothallium is a secondary formation, but this cannot be asserted
positively until the development is much better known than at
present, and its relation to the green prothallium of the Maratd-
aceae and the thallus of the Hepaticae must remain in doubt
The structure of the sexual organs and development of the
embryo point to a not very remote connection with the former
order, and in some respects also to the Anthoceroteae.

Ophioglossum beyond question shows the simplest type of
sporangium of any of the Pteridophytes, and may be directly
compared to a form like Anthoceros, In both cases the arche-
sporium is hypodermal in origin, and is formed without any
elevation of the tissue to form separate sporangia. In Antho-
ceros^ alternating with the sporogenous cells, are sterile cells
which divide the archesporium into irregular chambers containing
the spores. A direct comparison may be drawn between this
and the origin of the archesporium in Ophioglossum^ except that
in the latter the archesporium seems to be discontinuous,
and from the first separated into parts corresponding to the
separate sporangia. In some species of Ophioglossum^ too, the
epidermis above the sporangium has stomata as in Anthoceros.
A comparison of these remarkable points of similarity in the
structure of the sporophyll of Ophioglossum and the sporogoniura
of Anthoceros^ together with the ver>' simple tissues of the
former, led the writer ^ to express the belief that Ophioglossum^
' Bot, Gazette t Jan. 189a

IX MARA TTIA CE^—ISOETA CE^ 297

of all living Pteridophytes, seemed to be the nearest to the
Bryophytes. Subsequent study of the eusporangiate Ferns
has strengthened that belief, and from a comparison of these
with Ophioglossum on the one hand and the Anthoceroteae on
the other, it seems extremely likely that the latter represents
more nearly than any other group of living plants the form
from which the Pteridophytes have sprung, and that in the
series of the Filicineae at any rate, Ophioglossum comes nearest
to the ancestral form. Of course the possibility of Ophioglossum
being a reduced form must be borne in mind, and the sapro-
phytic habit of the prothallium may perhaps point to this ; still,
whatever may be its real character, there is little doubt that it
is the simplest of the Filicineae.

The resemblances between OpJUoglossum and the Anthocero-
teae are not confined to the sporophyte. The sexual organs —
and this is true of all the eusporangiate Pteridophytes — show
some most striking similarities that are very significant. It
will be remembered that in the Anthoceroteae alone among the
Bryophytes the sexual organs are completely submerged in the
thallus — the antheridia being actually endogenous. It will be
further remembered that in the eusporangiate Filicineae a similar
condition of things exists.

In all the Hepaticae the axial row of cells in the archegonium
terminates in the cover cell, which by cross-divisions forms
the group of stigmatic cells of the neck. In the Anthoceroteae
this terminal group of cells is the only part of the arch^onium
neck that is free, the lateral neck cells being completely fused
with the surrounding tissue. This arises from the arch^onium
mother cell not projecting at all, but we have seen that in
cross-section a similar arrangement of the cells is presented to
that found in the young archegonium of other Hepaticae. In
the Filicineae a similar state of affairs exists, but the divisions
in the mother cell are, as a rule, not so regular. Still, eg.
IsoeteSy it is sometimes easy to see that the mother cell (so-called)
of the archegonium is triangular when seen in cross-section, and
cut out by intersecting walls in exactly the same way as the
axial cell in the Bryophyte archegonium. In short, what is
ordinarily called the mother cell of the archegonium in the
Ferns is really homologous with the axial cell only of the young
archegonium of a Liverwort. A comparison of longitudinal
sections of the young arch^onium of Marattiuy for instance,

298 MOSSES AND FERNS chat.

with that of Notothylas, will show this clearly. From this it
follows that the four-rowed neck of the Pteridoph)^e archegonium
does not correspond to the six-rowed neck of the Bryophyte
archegonium, but only to the group of cells formed from the
primary cover cell, and is a further development of this. The
relatively long neck of the archegonium in the more speciaJised
forms, e.g, Botrychium Virginianuniy and especially the lepto-
sporangiate Ferns, must be regarded as a secondary develop-
ment connected probably with fertilisation. The shifting of
the archegonium to the lower surface of the gametophyte has
probably a similar significance. In B. Virginianuniy however,
the archegonia are borne normally upon the upper side of the
thallus, as in the thallose Liverworts.

It is possible that a similar relation exists between the
antheridia of the eusporangiate Ferns and that of the Antho-
ceroteae. In both cases the formation of the antheridium
begins by the division of a superficial cell into a cover cell and
a central one. The former divides only by vertical walls in the
MarattiacecBy but in Ophioglossum and the Anthoceroteae it
becomes two-layered. In the latter the central cell may form
a single antheridium, or it may produce a group of antheridia,
but in the others it divides at once into a mass of sperm cells.
By the suppression of the wall in the antheridium of an
Anthoceros where only one antheridium is formed, there would
be produced at once an antheridium of the type found in
Opkioglossunty and by a further reduction of the division of the
cover cell, by which it remains but one cell thick, the type
found in Marattia would result.

Such an origin of the antheridium of the Filicineae is, at
any rate, not inconceivable, while not so obvious perhaps as
the resemblances in the archegonium, and is simply suggested
as a possible solution of a very puzzling problem.

The Marattiaceae agree closely among themselves, and the
structure of the gametophyte is like that of the Ophioglossaceae,
so far as the latter is known, and also offers most striking
resemblances to the Hepaticae. The long duration of the
prothallium here, and its persistence after the sporophyte
is independent, as well as the long dependence of the latter
upon the gametophyte, are all indications of the low rank of
this order. The sporophyte, while showing many points of
resemblance to the Ophioglossacese, still differs very much

IX MARA TTIA CE^—ISOETA CE^ 299

also, and in general habit as well as the position of the
sporangia comes nearer the leptosporangiate Ferns. Of the
Ophioglossaceae, Helntinthostachys on the whole approaches
nearest to the Marattiaceae, so far as the general character
of the sporophyte is concerned. The venation of the leaves
and dehiscence of the sporangia are very similar to AngiopteriSy
and the green sterile tips to the sporangial branches hint at
a possible beginning of the lamina of the sporophylls in the
Marattiaceae. However, as the life-history of the plant and
its histology are almost unknown as yet, it is not possible to
draw any definite conclusion as to its affinities, and the question
wjiether the Marattiaceae are connected directly with the Ophio-
glossaceae, or have branched off from the same stock lower
down, must remain for the present unanswered ; but the
similarities in both sporophyte and gametophyte are too
numerous to make an entirely independent origin for the
two orders at all probable.

In seeking a connection with the leptosporangiate Ferns
there are two points where this is possible. The higher
species of Botrychium show an unmistakable approach to
the leptosporangiate type. The archegonium neck projects
much more than in the other Eusporangiatae, and the vascular
bundles in the petiole are truly concentric. The venation of
the leaves also becomes that of the typical Ferns. The
sporangia are completely free here, and smaller and more
delicate, although truly eusporangiate in development. In all
these respects there is an approach to Osmundaj unquestionably
the lowest of the leptosporangiate series. Helntinthostachys
too may be almost as well compared to Osmunda as to
Angiopteris,

On the other hand, in the circinate vernation of the leaf
as well as the histology, in the roots, and in the sporangia,
the Marattiaceae, especially AngiopteriSy approach quite as
close or closer to the Osmundaceae than does Botrychium or
Helntinthostachys.

Isoetes differs so much from all other Pteridophytes that
it seems almost hopeless to try to assign it its proper position
in the series. The reasons for assigning it to the Filicineae
rather than the Lycopodineae, are first the character of the
gametophyte and sexual organs, and second the histology of
the mature sporophyte. The archegonium resembles very

300 MOSSES AND FERNS chap,

closely that of the other eusporangiate Filicineae, and the
spermatozoids are multiciliate, which is never the case in any
of the Lycopodineae, but is universal in the Ferns. The
tissues of the sporophyte, especially the vascular bundles, are
collateral, and are most like those of Ophioglossunty and the
dichotomy of the roots, which was formerly taken as a sign
of its relationship with the Lycopods, is now known to occur
also in Ophioglossum, The sporangium, too, may perhaps as
well be compared to the spike of Ophioglossum as to the single
sporangium of Lycopodium or Lepidodendron, It would be
rash to assert positively that the trabeculae correspond to
the partitions between the sporangia of Ophioglossum^ and
that the sporangium is really compound, but this is not
inconceivable. The position and origin of the large spor-
angium of Isoetes are certainly not very unlike those of the
sporangiophore of Ophioglossum.

The early stages in the development of the female pro-
thallium certainly resemble those of Selaginella, so far as the
" free-cell formation " is concerned ; but there is no reason why
this may not have arisen independently in the two groups,
just as heterospory arose quite independently in all the
classes of the Pteridophytes. At present, then, the weight
of evidence seems to indicate that Isoetes bears the same
relation, but in a much more remote degree, to the lower
members of the eusporangiate Filicineae that SelagineUa does
to Lycopodium.

As to the affinities of Isoetes with the Spermaphytes, it
more nearly resembles them in the formation of the female
prothallium than any other Pteridophyte except SelagineUa,
and the reduction of the antheridium is even greater than
there. The embryo resembles very much that of a typical
Monocotyledon, and the histology of the fully -developed
sporophyte, the leaves with their sheathing bases surrounding
the short bulb-like stem, and the structure of the roots, all
suggest a possible relation to the Monocotyledons directly
rather than through the Gymnosperms.

There is, however, a great interval between the flower of
the simplest Angiosperm and the sporophylls of Isoetes, and
more evidence must be produced on the side of the former
before it can be asserted that this relationship is anything
more than apparent.

IX MARATTIACE^—ISOETACE^ 301

We may conclude, then, from the data at our disposal,
that the living eusporangiate Filicineae consist of a few
remnants of widely divergent branches of a common stock,
which formerly was predominant, but has been supplanted by
more specialised modern types. From this primitive stock
have arisen on the one hand the leptosporangiate Ferns, on
the other, through IsoeteSy or some similar heterosporous forms,
the Angiosperms.

CHAPTER X

FILICINE^ LEPTOSPORANGIATyE

The Leptosporangiatae bear somewhat the same relation to- the
eusporangiate Ferns that the Mosses do to the Hepaticae, but
the disproportion in numbers is much greater in the former case.
While the whole number of living Eusporangiatae (including
Isoetes) is probably considerably less than lOO, the Lepto-
sporangiatae comprise about 3500 species. In the former the
differences between the groups are so great that there is some
question as to their near relationship, while all the leptospor-
angiate Ferns show a most striking similarity in their structure,
and except for the presence of heterospory in two families,
might all be placed in a single order. Carrying our com-
parison still further, we may compare the Polypodiaceae, which
far outnumber all the others, with the Bryineae among the
Mosses. Both groups are apparently modern specialised types
that have supplanted to a great extent the lower less specialised
ones.

The distribution of the leptosporangiate Ferns, too, offers
some analogy with the Mosses. While the eusporangiate
Ferns are few in number of species, they are for the most part
also restricted in nunibers of individuals and in their range.
The Leptosporangiates, on the other hand, occur in immense
numbers, especially in the tropics, where they often form a
characteristic feature of the vegetation. This is true to a
limited extent in temperate regions also, where occasionally a
single species of Fern, e,g, Pteris aquilina^ covers large tracts of
ground almost to the exclusion of other vegetation. A some-
what prevalent idea that the Ferns of to-day form merely an
insignificant remnant of a former vegetation is hardly borne

CHAP. X FILICINEA^ LEPTOSPORANGIAT.E 303

out by the facts in the case. Any one who has seen the
wonderful profusion of "Ferns in a tropical forest, and the
enormous size to which many of them grow, is very quickly
disabused of any such notion.

The fossil record is also extremely instructive as bearing on
this point. According to Solms-Laubach ^ there is but one
certainly authentic case from the Carboniferous rock which can
be regarded certainly as a leptosporangiate form, all of the
other sporangia discovered being of the eusporangiate type.
In the later formations the Leptosporangiates increase in
number, but according to Luerssen ^ undoubted Polypodiaceae
are not found before the Tertiary, where a number of living
genera are represented. That is, so far as we can judge from
the. fossil record, the Leptosporangiatae, instead of being a left-
over type, are essentially a modern one.

Except in the few heterosporous forms there is, on the
whole, great uniformity in the prothallium. The most marked
exception to this is the well-known filamentous protonema-like
prothallium of some species of Trichomanes. Except in these,
however, the germinating spore, either directly or after forming
a short filament, produces normally a flat, heart-shaped pro-
thallium, growing at first by a two-sided apical cell, the pro-
thallium being at first one cell thick, but later producing a
similar cushion to that found in Marattia but less prominent,
and the wings always remain one cell thick. Upon the lower
side of the cushion are produced the archegonia, which have
always - a projecting neck, sometimes straight, but more com-
monly bent backward. The antheridia are produced upon the
same prothallium as the archegonia in most forms, but a few
species of Ferns are dioecious, and usually there are small male
prothallia in addition to the large hermaphrodite ones. The
antheridia, like the archegonia, always project above the pro-
thallium.

The heterosporous genera, as in Isoetes, produce two sorts
of prothallia, but the male prothallium is not so much reduced,
and the female is formed by successive cell divisions and not
by free cell formation.

The first divisions in the embryo always divide it into
regular quadrants, and the young members always grow from
a definite apical cell, which, with the possible exception of some

' Solms-Laubach (2), p. 153. '•* Luerssen (7), voL ii. p. 574.

304 MOSSES AND FERNS chap.

of the Osmundaceae, is also found at the apex of the later roots
and always in the stem. In size the sporophyte varies ex-
tremely. In some of the smaller Hymenophyllaceae the
creeping stem is not thicker than a common thread, and the
fully -developed leaves scarcely a centimetre in length. The
other extreme is offered by the giant tree-ferns belonging to
the Cyatheaceae, e,g. Alsophila^ Cyathea^ Cibdiiunt, The leaves
are in most cases compound, and either firm and leathery in
texture, or in the delicate Hymenophyllaceae have the lamina
reduced to a single layer of cells, so that in texture it recalls a
moss leaf. With the single exception of the Salviniaceas the
leaves are always circinate in the bud. The surface of the
stem and leaves is frequently provided with various epidermal
outgrowths, scales, and hairs, which show a strong contrast to
the mostly glabrous Eusporangiatae. The vascular bundles
are, both in the stem and petioles, of the concentric type with
a very distinct endodermis, and in the older parts of both
stems and leaves parts of the ground tissue are often changed
into thick-walled and dark-coloured sclerenchyma. In the finer
veins of the leaf the vascular bundles are reduced in structure
and more or less perfectly collateral.

The sporangia are extremely uniform in structure through-
out the group. They can be traced back to a single epidermal
cell, in most cases developed from the lower side of the un-
modified sporophylls, as in the Marattiaceae. They are always
more or less distinctly stalked, and grow for a time from a
pyramidal apical cell, whose growth is stopped by the formation
of a periclinal wall (Fig. 167). The central tetrahedral cell
has first a layer of tapetal cells cut off from it, and the central
cell then forms the archesporium. No sterile cells are formed
in the archesporium, but all the cells (except in the macro-
sporangium of the Hydropterides) develop perfect spores. The
ripe sporangium is provided, except in the Hydropterides, with
an annulus or ring of thickened cells, which assists in its
dehiscence, and forms the most characteristic structure of the
ripe sporangium.

Non- Sexual Reproduction

In a few of the Ferns special non-sexual reproductive bodies,
buds of different kinds, occur upon the prothallium, which thus

X FILICINE^ LEPTOSPORANGIAT^ 305

may have an unlimited growth. Such buds may have the
form of ordinary branches, or they are of a special form.
Buds of the latter class occur, sometimes in great numbers, in
certain Hymenophyllaceae, where they are formed upon the
margin of the prothallium, to which they are attached by short
unicellular pedicels from which they readily become detached.
In this way, as well as by the separation of ordinary branches,
the prothallia of some species of Hymenophyllum form dense
mats several inches in diameter, which look exactly like a
delicate Liverwort. A most remarkable case is that of Gymno-
gramme leptophylla^ examined by Goebel.^ The prothallium
multiplies extensively by buds, some of which form tuber-like
resting bodies, by which the prothallium becomes perennial.
The sporophyte in this species is annual and dies as soon as
the spores ripen. The archegonia are borne on special branches
of the prothallium, which penetrate into the ground and lose
their chlorophyll. Goebel ^ suggests what seems very probable,
that the subterranean prothallium of the Ophioglossaceae may
be of this nature, and the fact that in Botrychium Virginianum
the germinating spore develops chlorophyll would point to this.

Apogamy, or the development of the sporophyte from the
prothallium as a vegetative bud, was first discovered by Farlow ^
and later investigated by De Bary,^ Leitgeb,^ and Sadebeck.^
It is known at present in Pteris Cretica^ Aspidium filix-mas
var. cristatum, Aspidium falcatum^ Todea Africana^ and several
others. Sometimes archegonia are produced, or they may be
absent from the apogamous prothallium, but antheridia usually
are found. When archegonia are present they do not appear
to be functional. In Pteris Cretica^ where usually no archegonia
are developed, the cushion of tissue which ordinarily produces
them is formed as usual ; but instead of forming archegonia it
grows out into a leaf at whose base is formed the stem apex,
which soon produces a second leaf. The first root arises
endogenously near the base of the primary leaf, and the young
plant closely resembles the sporophyte produced in the normal
way. Previous to the development of the bud there is formed in
the prothallium itself a vascular bundle which is continued into
the leaf, but which is entirely absent from normal prothallia.

The opposite state of affairs, where the gametophyte arises

' Goebel (i). * Goebel (10), p. 245. » Farlow (i).

* Dc Bary (2). ' Leitgeb (13). « Sadebeck (6), p. 231.

3o6 MOSSES AND FERNS chap.

directly from the sporophyte without the intervention of spK>res,
is known in a number of species, and has been especially
investigated by Bower.^ He found that there were two types
of aposporyy as he named the phenomenon, one where the
prothallium was produced from a sporangium arrested in its
normal growth, and by active multiplication of the cells of the
stalk and capsule wall formed a flattened structure, which soon
showed all the characters of a normal prothallium with sexual
organs. In the second case the prothallia grew out directly
from the tips of the pinnae, and there was no trace of sporangia
being formed previously. The first observation of these
phenomena were made upon two garden varieties, Athyriumfilix'
fcemina var, clarissima and Polystichum angulare var. pulcfierrt-
munty but since, Farlow ^ has discovered the same phenomenon
in Pteris aquilina. In the latter the prothallia were always
transformed sporangia.

The production of secondary sporophytes as adventitious
buds upon the sporophyte is a regular occurrence in some
species. Asplenium bulbiferum and Cystopteris bulbifera are
familiar examples of such sporophytic budding. In these large
numbers of buds are formed which soon develop all the
characters of the perfect sporophyte. Very early a definite
apical cell is established from which all the other parts are
derived. In Camptosaurus rhizophyllus^ the " walking fern " of
the Eastern United States, a single bud is formed at the tip of
the slender leaf which bends over until it takes root. From
this terminal bud another leaf grows and roots in the same
way.

Classification of the Leptosporangiatce

The Leptosporangiatae fall into two groups, which may be
termed orders, although the two families in the second order
(Heterosporeae) are not closely related to each other, but each
has nearer affinities with certain of the homosporous forms.

I. Homosporous forms with large green prothallium, usually
in its early stages growing from a single apical cell, more
commonly monoecious but sometimes dioecious. Leaves always
circinate in vernation. Sporangia with a more or less developed
annulus, either borne upon ordinary leaves or on specially
1 Bower (6). « Farlow (2).

X FILICINE^ LEPTOSPORANGIATA^ 307

modified sporophylls. Usually, but not always, each group of
sporangia (sorus) covered by a special covering, the indusium.
Order I. Filices.

Family i. Osmundaceae.
Family 2. Gleicheniaceae.
Family 3. Hymenophyllaceae.
Family 4. Schizaeaceae.
Family 5. Cyatheaceae.
Family 6. Polypodiaceae.

11. Heterosporous forms, either aquatic or amphibious ; the
prothallia are always dioecious, the female prothalHum with
chlorophyll and capable of more or less independent gipwth
when not fertilised ; male prothallium always without chloro- •
phyll, the vegetative part reduced to one or two cells, besides
the antheridium. Leaves__either ^ircinate (M^rsifiaceae) or
folded ^Salviniafepe) ; sporangia without an annulus and borne
in special " sporocarps," whjchjre eit}ier^jpodi fied branches of

^^^ii5?£Z_J.^Sy-^^-- i^^ili??^^) ^^ .^ ^^O^ highly developed
indusium.

Order II. Hydropterides.

Family i. Marsiliaceae.
Family 2. Salviniaceae.

Order L Filices

The six families of the Filices form an evidently very
natural group, but there has been a good deal of disagreement
as to their relative positions. The Osmundaiceae are generally
recognised as approaching most nearly the eusporangiate Ferns,
and the Gleicheniaceae come next to these. The Hymeno-
phyllaceae are usually considered at the other extreme of the
series, but there are a number of reasons why this seems doubtful,
and I am inclined to assign them an intermediate position.
Their structure and development give evidences of their being
a specially modified group adapted to living in very damp
situations, and they probably cannot be regarded as connecting
any of the other families, but rather as a side branch which has
developed in a direction away from the type. They come
nearest the Gleicheniaceae and Osmundaceae in the structure of
the sexual organs, and the sporangium shows points in common

3o8 MOSSES AND FERNS chap.

with the former family. It, however, also resembles that of the
Cyatheaceae as well, and the strongly -developed indusium is
much like that of the latter. The Schizaeaceae also may
possibly form a side branch from the ascending series which
ends in the Polypodiaceae.

As these latter are the typical modern Ferns, it will be best
to trace the development of the plant here before considering
the variation found in the other families. The spores of the
genus Onoclea are especially suited to studying the germination
and development of the prothallium, and we will follow this
in O, struthiopteris {Struihiopteris Germanica)^ the well-known
Ostrich Fern.

The large oval spores contain, besides much oil and some
starch, numerous small crowded chloroplasts. The three walls
of the spore are plainly demonstrable, especially as the brown
perinium is often thrown off by the swelling of the spore, and
the transparent exospore can then be seen, with the delicate
endospore lying close to its inner face. A large nucleus
occupies the centre of the spore. Contrary to the statements
usually made that spores containing chlorophyll quickly lose
their vitality, these will germinate after a year or more, although
not so well as those of the same season, but they normally
remain from autumn until spring before they germinate. O.
sensibilis acts in the same way, and spores of other Ferns
containing chlorophyll have been germinated after an equally
long period.

The spores germinate promptly, varying from two or three
days to about a week, depending upon the temperature. The
exospore is ruptured irregularly near one end, and through this a
short colourless papilla protrudes and is shut off by a transverse
wall (Fig. 156, B). This papilla contains little or no chloro-
phyll and rapidly lengthens to form the first root-hair, which
undergoes no further divisions. The large green cell alone
produces the prothallium. The divisions in the prothallial
cell vary somewhat, but in the great majority of cases a series
of transverse walls is first formed, and the young prothallium
(Fig. 156, C) has the form of a short filament. Sooner or
later, in normally-developed prothallia, the terminal cell of the
row becomes divided by a longitudinal wall, which may be
straight, but more frequently is oblique and followed by another
similar wall in the larger of the two cells, meeting it so as to

FILICINE^ LEPTOSPORANGIAT^

309

include a triangular cell, which is the " two-sided " apical cell of
the next phase of the prothallium's growth. The divisions up

Fig. x^t.—OnocUa struthwpUris (Hoffm). A, B, Germinating spores with the perinium removed,
X 3<» ; C, young prothallium, X 100 ; D, E, older prothallia with two-sided apical cell (x), X 300 ; F,
small female pwthallium seen from below, X 35 ; G, very young prothallium with the two outer
spore-coats, X 300 ; r, primary rhizoid ; ar^ archegonia ; /, perinium ; rx, exospore.

to this point correspond exactly with those of Aneura or
Metzgeria^ and are also much the same as in Marattia, except

3IO MOSSES AND FERNS chap.

that here the prothallium only in very rare cases assumes the
form of a cell mass at first.

By the regularly alternating segments of the apical cell
the young prothallium soon assumes a spatulate form, which
becomes heart-shaped by the rapid growth of the outer cells of
the young segments, which grow out beyond the apical cell.
Sooner or later the single apical cell is replaced by two or
more initials formed from it in the same way as in the
Marattiaceae, and from this time on the growth is from a series
of marginal initials. This change is connected with the
formation of the thickened archegonial cushion, which, so far as
I have observed, does not form in Onoclea so long as the single
two-sided apical cell is present.

As the prothallium grows new root-hairs grow out from
the marginal and ventral cells and fasten the prothallium firmly
to the ground. These hairs, colourless when first formed, later
become dark brown.

In the genus Onoclea^ as well as some other Polypodiaceae,
the prothallia are regularly dioecious, and only a part of them
develop the archegonial meristem. The others remain one-
layered, and are often of very irregular form, and may be
reduced to a short row of a few cells. In Athyrium filix-
fcemina these may even be reduced to a single vegetative cell
besides the root-hairs, and an antheridium. Cornu^ records
similar reduced prothallia in Aspidium filix-mas. All of the
" a-meristic " prothallia, as Prantl * calls them, are males. In
the majority of the Polypodiaceae these occur more or less
plentifully, and are often the result of insufficient nutrition ;
but in Onoclea it is something more than this, as not only the
small prothallia are male, but the large ones are exclusively
female, and not hermaphrodite, as in most Ferns.

The first antheridia appear within three or four weeks under
favourable conditions, and are formed either from marginal or
central cells of the prothallium. The very young antheridium
is scarcely to be distinguished from a ypung root-hair. Like it,
it arises from a protrusion of the cell which is cut off by a wall,
which is usually somewhat oblique. The papilla thus formed
enlarges and soon becomes almost hemispherical. It contains
a good deal of chlorophyll and a large central nucleus surrounded
by dense cytoplasm. The first wall in the young antheridium

' Cornu (i). 2 Prantl, Flora, 1878, p. 499.

FILICINE^ LEPTOSPORANGIATjE

(Fig.' 157, A) is very peculiar. It has usually the form of a
funnel, whose upper rim is in contact with the wall of the
antheridium cell, and whose base strikes the basal wall of the
antheridium. Sometimes this first wall does not reach to the
base, in which case it is simply more or less strongly concave,
and the basal cell cut off by it from the antheridium is discoid

Fig. \n.—Onoclea siruihiopteris (HoffmX Development of the antheridium. A-C, Vertical sections,
x6oo ; D, two nearly ripe sperm cells ; £, free spermatozoid, X 1200 (about).

instead of ring-shaped (Fig. 157, B). The second wall is
hemispherical, and is nearly concentric with the outer wall of
the antheridium. The dome-shaped central cell produces the
mother cells of the spermatozoids, and has much more dense
contents than the outer cells, but all the chloroplasts remain in
the latter. A third wall now forms in the upper peripheral
cell, much like the first one in form, and cuts off a cap cell at

312 MOSSES AND FERNS chap.

the top. The young antheridium at this stage consi^s of
four cells — a central dome-shaped one surrounded by three
others, the two lower ring-shaped, and the terminal one discoid.
These outer cells are nearly colourless, and contain very little
granular contents, except the small chloroplasts, which are
mainly confined to the surface of the inner walls.

The divisions in the central cell are at first very regular.
The first one is always exactly vertical, and is followed by a
transverse wall in either cell which strikes it at right angles,
and next a third set of walls at right angles to both of these,
so that whether seen in cross-section or longitudinal section,
the central cells are arranged quadrant- wise. Successive bi-
partitions follow in all the cells until the number may be a
hundred or more, but the number is usually much less, about
thirty-two being the commonest. The regular arrangement of
the sperm cells soon becomes lost, and they form a mass of
polyhedral cells with dense granular cytoplasm, and lai^e
nuclei. A nucleolus is visible until the last division, after
which it can no longer be distinguished ; otherwise the nuclei
show no peculiarities. The transformation of the nucleus into
the body of the spermatozoid proceeds here as in other Ferns
that have been examined, but I was unable to satisfy myself
that so large a part of the forward end of the spermatozoid is
of cytoplasmic origin, as Strasburger^ asserts. The fully-
developed spermatozoid describes about three complete coils
within the globular sperm cell, and does not lie coiled in a
single plane, as in the Hepaticae, but in a tapering spiral (Fig.
157, D). The very numerous long cilia are attached at a
point a short distance back from the apex, and as Buchtien '
showed, cover a limited zone, although hardly so restricted as
he figures.

The separation of the sperm cells begins at about the time
the development of the spermatozoids commences. The
mucilaginous walls stain now very strongly, and in a living
state appear thick and silvery-looking. The central lamella
of the cell wall, however, remains intact, so that when the
spermatozoids are ejected, they are still enclosed in a delicate
cell membrane, which swells up as the water is absorbed and
finally dissolves completely. The vesicle derived from the
remains of the cytoplasm is very conspicuous here, and the

* Strasburger (ii), vol. iv. p. 115. ' Buchtien (1), p. 38.

FILICINE^ LEPTOSPORANGIAT^

3»3

granular contents usually, but not always, show the starch re-
action. The body of the free spermatozoid has the form of a
flattened band with thickened edges, which tapers to a fine
point at the anterior end, but is broader and blunter behind.
The peripheral cells of the antheridium become so much
compressed by the crowding of the sperm cells that they are
scarcely perceptible, but after the antheridium is burst open, the
two lower ones become so distended that they nearly fill the
central cavity. The opening is effected either by a central
rupture of the cover cell, or less commonly by a separation of
this from the upper ring cell.

Fig. xiZ.—Onoclea $truthwpteris (Hoflfm). A, Longitudinal section of the apex of a female pro-
thallium, showing the apical cell {x) and a nearly ripe archegonitun, Xai5 ; B-D, development of
the archegonlum ; longitudinal sections, X 430 ; A, neck canal cell.

The development of the archegonium is intimately connected
with the apical growth of the large female prothallium. As
soon as the single apical cell has been replaced by the marginal
initials, the divisions in the latter become very definite. Com-
parison of cross and longitudinal sections shows that these are
much like those of Marattia or, among the Hepaticae, Dendroceros
or Pellia epiphylla. Each initial cell has the form of a semi-disc
(Fig. 158, A), and the growth is both from lateral segments,
which mainly go to form the wings of the prothallium, and
basal, or inner segments, which produce the projecting arche-

314

MOSSES AND FERNS

gonial cushion. If this begins to form very early, it may form
a midrib extending nearly the whole length of the prothallium ;
but usually it does not form until relatively late. Each basal
segment of the initial cells divides into a dorsal and ventral
cell (semi-segment), the latter the larger of the two, and with
much more active growth. The latter alone is concerned in
the growth of the projecting cushion. Each ventral semi-
segment is first divided by a wall parallel with the primary
segment wall, and from the anterior of these cells, almost
exactly as in Notothylas^ the archegonium is developed. It is

not possible to make out any definite
succession of walls by which the
axial cell of the archegonium is cut
out, but it soon is recognisable by the
granular cytoplasm and large nucleus.
As in Marattia^ the first transverse
wall separates the inner cell from the
cap cell, and the inner one then
divides into the basal and the central
cells. The cover cell divides into
the four prima^ry neck cells, and the
central cell arching up between these
has the pointed apex cut off by a
curved wall from the central cell.
The primary neck canal cell, so
formed, is noticeably smaller than
that of Marattia, The neck cells,
which in the eusporangiate forms all
grow alike, here show a difference,
and the two anterior rows develop
faster than the posterior ones, so that these rows are longer and
the neck is strongly bent backward. In Onodea there are
usually about seven cells in each anterior row and about two less
in the posterior ones. The neck cells are almost colourless,
with distinct nuclei, and a few small, pale chloroplasts. From
the central cell is now cut off the ventral canal cell, which is
quite small, and separated from the egg by a strongly concave
wall. The nucleus of the neck canal cell always divides, but
no division wall is formed, and the two nuclei lie free in the
cell. The basal cell divides by cross-walls into four, and with
similar cells cut off from the adjacent prothallial tissue forms

Fig. 159.— Ripe archegonium of O.
stmthiopteris in the act of open-
ing, X 300 ; <?, the egg.

X FILICINE^ LEPTOSPORANGIAT^ 315

the venter of the ripe archegonium. The disintegration of the
division walls of the canal cells, and the partial deliquescence of
the inner walls of the neck cells, offer no peculiarities.

When the archegonium opens, the terminal cells diverge
widely and the upper ones are often thrown off.

The opening of the sexual organs and the entrance of the
spermatozoids may be easily seen by simply allowing the plants
to remain slightly dry for a few days until a number of sexual
organs are mature. If these are now placed upon the slide of
the microscope in a drop of water, in a few minutes the sexual
organs will open, and the spermatozoids will be seen to be
attracted to the archegonia in large numbers, and with care
some of them may be followed into the neck and down to the
central cell. The actual entrance of the spermatozoid into the
egg has been observed, but is difficult to demonstrate in the
living condition. Pfeffer ^ has shown that the substance which
attracts the spermatozoids in the Polypodiaceae is malic acid,
and that an artificial solution of this, of the proper strength,
will act very promptly upon the free spermatozoids of these
Ferns.

As soon as the egg is fertilised it develops a membrane,
and soon after undergoes its first segmentation. The inner
walls of the neck cells almost immediately turn dark brown,
and the cells of the ventral part begin to divide actively and
form the calyptra, which here, as in the Bryophytes, is formed
from the venter alone, and is tipped with the remains of the
neck cells.

The position of the archegonium depends largely upon the
light. If both sides of the prothalHum are about egually
illuminated, archegonia will develop from both sides. As soon
as an archegonium is fertilised, no new ones form, but it
frequently happens that a very large number prove abortive
before finally fertilisation is effected.

The Embryo

The first division wall in all Polypodiaceae yet investigated
is vertical and nearly coincident with the axis of the
archegonium. This basal wall (Fig. 160, I) at once divides
the embryo into the anterior epibasal half and the posterior

» Pfeffer (3).

3i6

MOSSES AND FERNS

CHAP.

hypobasal. The former produces the stem and cotyledon, the
latter the primary root and foot. The early divisions are
extremely regular, and offer a marked contrast to those in the
eusporangiate embryo. The second wall is the transverse
(quadrant) wall, separating the leaf and stem in the epibasal

Fig. i6a — A, Median longitudinal section of a young embryo of Adiantum concinmtm (H. B. K-)
(after Atkinson) ; B, a four-celled embryo of O. strutkiopteris ; C, an older embryo of the same
in nearly median section, X 250 ; */, stem ; R, primary root ; L, cotyledon ; F, foot.

part, and the root and foot in the hypobasal. The next walls
are the median or octant walls, but they do not correspond
exactly in all the quadrants. While in the cotyledon and stem
they are almost exactly median, in the root especially the
octant wall diverges often a good deal from the median line.

X FILICINE^ LEPTOSPORANGIAT^ 317

and the two resulting octants are unequal in size. The follow-
ing divisions correspond for a short time in all the octants, but
soon show characteristic differences. For a short time each
octant shows a definite apical growth, the segments being cut
off by walls formed successively parallel to the three primary
divisions in the embryo, so that each octant may be said to
have a three-sided apical cell. When the octant wall in the
root quadrant is decidedly oblique this is not always evident in
the smaller octant, and the larger one in this case at once
becomes the definitive apical cell of the primary root.

The first of these walls is usually parallel to the basal, the
second to the quadrant wall. Sometimes this order is reversed,
but never, apparently, is the first wall parallel with the octant
wall. Before the third segment is cut off from the octant, each
of the two first ones divides by a periclinal wall into an inner
and an outer cell. Each octant now consists of five cells, two
inner and three outer ones, of which one is the primary octant
cell, which still retains its original tetrahedral form. The
outer cell of each segment divides by a radial wall, but beyond
this the succession in the walls differs. Of the eight original
octants, one in each quadrant persists as the apical cell respectively
of cotyledon, stem, root, and foot, but in the latter it becomes
very early obliterated by the formation of a periclinal wall and
further longitudinal divisions, which is the case also with one of
the octants in the leaf and root. In the stem both octants
persist, one becoming the permanent stem apex, the other
forming the apical cell of the second leaf.

The Cotyledon

Of the two primary octants of the cotyledon, one very early
ceases to grow and soon becomes indistinguishable, and the
subsequent growth is due almost entirely to the activity of a
single octant. The apical cell is at first like that of the other
members, tetrahedral, but after about two sets of segments
have been cut off from it no more are usually cut off from the
side of the apical cell parallel to the basal wall, and the three-
sided cell thus passes over into a two-sided one with segments
cut off alternately right and left. By the suppression of the
growth in the sister octant, the apical cell gradually assumes a
nearly median position. By the change to the two-sided form

3i8

MOSSES AND FERNS

of the apical cell, the originally conical leaf rudiment becomes
flattened, and a little later this is followed by a dichotomy of
the growing point and the production of two apical celjs like
the original one (Fig. i6i, C). The division is first brought
about by a nearly central longitudinal division of the apical
cell, and on either side of this, by a curved wall running to the
outer wall of each cell, two new apical cells, separated by two
elongated central cells, result. Each of these new growing
points develops one of the lobes of the cotyledon, which undergo
one or more bipartitions before the cotyledon breaks through

A. ^ C.

Fig. i6x. — Onoclea struthiopieris (HofTm). A, Longitudinal section of young sporophyte still con-
nected with the prothallium {pr\ X 60 ; B, the apex of same, X 180 ; C, surface view of the young
cotyledon showing the first dichotomy ; D, central region of A, showing the primary tradieary
■ tissue, Xx8o ; E, young sporophyte with nearly full-grown cotyledon and primary root, x 3 : //,
stem ; L*, cotyledon ; L*, second leaf ; F, foot ; /f , prothallium.

the prothallium. As in Marattia the growth is much stronger
upon the outer side and the leaf strongly curved over. It very
early grows beyond the stem apex, and the embryo loses its
oval form much earlier than is the case with any of the
Eusporangiatae.

TJie Stem

The early segmentation of the stem apex is much the same
as in the cotyledon ; but later the divisions in the segments are

X FILICINE^ LEPrOSPORANGIAT^ 319

somewhat different, and the first wall is a radial one, instead of
periclinal. The stem is very short at the time the young
sporophyte breaks through the prothallium, and its apex more
pointed than is afterwards the case.

Tlie Root

At first the segmentation of the apical cell of the root is
almost exactly like that of the stem, and it is not untiL several
lateral segments, usually about two series of them, have been
formed that the first periclinal wall, cutting off the first cell of
the root-cap, is formed. There is a good deal of difference,
however, as to the time this occurs, and there is probably some
connection between it and the different period at which the
primary root breaks through the calyptra. In most Poly-
podiaceae the root is the first of the organs to penetrate the
calyptra, but sometimes in Onoclea it is still short at the time
the cotyledon is nearly developed, and in this recalls Marattia^
where this is regularly the case. As soon as the first segment
of the root -cap is formed, the segmentation of the root is
extremely regular, and corresponds essentially to that found in
the later roots.

The Foot

All definite divisions cease very soon in both of the foot
octants, and this part of the embryo forms a more or less
projecting hemispherical mass of cells, closely appressed to the
prothallial cells. As usual in such cases the outer cells are
large and distinct.

Shortly before the embryo breaks through the calyptra,
which takes place much earlier than in Marattia^ the first traces
of the vascular bundles are seen as strands of procambium cells
occupying the axis of each of the primary organs, and united in
the centre, so that the four bundles together form a cross. Of
these the one going to the foot is short, and ends blindly within
that organ, but the others continue to grow with the elongation
of the members to which they belong. The first permanent
tissue to be recognised forms, as in Marattiuy a bundle of short
irregular tracheids at the junction of the young bundles
(Fig. 161, D). These primary tracheids in Onoclea are
scalariform, but the pits are shorter than in the later ones.

320 MOSSES AND FERNS chap.

Throughout the life of the sporophyte no vessels are formed,
but only tracheids, as in nearly all Ferns. In the cotyledons
the tracheids are all spiral, and occupy the centre of the con-
centric bundle, and from these growth proceeds centrifugally.
The elements of the phloem are poorly differentiated, and in this
stage no true sieve-tubes could be detected. While a definite
bundle -sheath can scarcely be made out, the limits of the
bundle are clearly defined. The venation of the cotyledon is
dichotomous, corresponding to the dichotomous branching of
the lamina.

The bundle of the young stem is solid, and is mainly
composed of short and broad scalariform tracheids, but in the
centre of the bundle are some small spiral and reticulate ones.
The phloem at this stage is not well developed, and does not
show perfect sieve-tubes.. The bundle sends a branch to the
second leaf, but is continued beyond the point of contact, and
develops tracheids above the point of union before the first
ones are formed in the leaf. In this early stage the bundle-
sheath is very poorly differentiated in the stem, but becomes
better marked as the plant develops.

The primary root is monarch, and the tracheary tissue
composed of short pointed tracheids with irregular scalariform
markings. These are surrounded by one or two layers of
narrow cells with oblique transverse septa. The calyptra is
soon penetrated by the cotyledon, which, instead of growing
straight up through the prothallium, as it does in Marattia^
breaks through upon the ventral side and then bends upward
between the lobes in front (Fig. i6i, E). The root bends
down and penetrates the earth, and very soon after the
prothallium dies. The epidermis of the cotyledon produces
small glandular hairs, and that of the root numerous root-hairs.

The second leaf is directly traceable to one of the primary
stem octants, and may be either regarded as one of the primary
members of the embryo, or as the first segment of the stem.
Its development corresponds exactly to that of the cotyledon,
as it does in its fully-developed state. The second root arises
endogenously, like all the later ones, and its apical cell is formed
close to the point of union of the bundles of the leaf and stem,
and probably, as in the later roots, is derived from a cell of the
endodermis.

The new leaves arise in regular succession from the segments

X FILICINE^ LEPTOSPORANGIA T^ 32 1

of the apical cell of the stem and up to the fifth or sixth, and
possibly later the first division of the leaf is dichotomous, and
the pinnate form of the later leaves is gradually attained, as in
Marattia. As the stem grows its vascular cylinder becomes
better developed, and a distinct endodermis becomes evident,
and it gradually passes over from the monostelic condition of
the young plant to the polystelic form found in the adult. A
cross-section of a plant with three fully-developed leaves showed
the vascular cylinder to be oval in outline, and consisting of the
following parts. A central pith of elongated parenchymatous
cells, surrounded by a thick ring of short spiral and reticulate
tracheids, outside of which was a zone of phloem, the whole
enclosed by a distinct endodermis. The latter is continuous,
with the endodermis of the bundles going to the leaves and
roots, and the xylem of these also connects with those of the
stem bundle. The apex of the stem becomes more and more
hidden by the development of scales from the epidermis, which
finally completely hide it and form a very eflRcient protection.

The petioles of the first three leaves have a single axial
vascular bundle, but in the fourth, as in all subsequent ones,
there are two. They separate very soon after leaving the stem
bundle, which is deeply cleft where they issue from it. These
bundles are typically concentric in structure, and have a well-
developed endodermis. The number of roots in the young
plant exceeds the leaves. In a plant with the fourth leaf still
unfolded, there were six fully-developed roots.

The Mature Sporophyte

The Stem

The stem in most of the Polypodiaceae is either an erect or
creeping rhizome which, unlike that of the Eusporangiatae, often
branches freely. These branches are always formed mono-
podially, and are usually of the same structure as the main
axis ; but in O. struthiopteris great numbers of peculiar stolons
are formed that are quite different at first in appearance from
the ordinary shoots. The main axis in this species is an
upright rhizome about 2 cm. in diameter, but appearing much
larger on account of the thick persistent leaf-bases which cover

322

MOSSES AND FERNS

CHAP.

it. The stolons arise from the bases of these leaves, apparently
as adventitious buds. They may remain dormant for a long
time, as very many more of the very small ones are found than
those that are fully developed. These finally bend upward,
and the scattered scale-like leaves give place to the perfect
green ones. The main rhizome is occupied by a central
cylinder composed of a network of anastomosing bundles.
Inside of this cylinder is a medulla made up of large parenchyma

Fig. 162.— a, Vertical longitudinal section of the apex of a rhizome of Adiantum emargituUmm
(Bory)* X25 ; B, the central part of the same, X 180 ; L, a young leaf; C, cross-section of a
similar stem apex, X x8o ; D, apex of a young leaf of Onodta struthiopttru^ showing the apical
cell (;c).

cells, and communicating with the cortex by means of the
foliar gaps, or spaces between the bundles.

Fig. 162, A shows a longitudinal section of the apex of a
stem of Adiantum emarginatumy which shows the typical appear-
ance in the Polypodiacea;. The apex of the stem forms a
slight cone, whose centre is occupied by the large initial cell,
which is deeper than broad. In cross-section it shows much
the same form. Divisions occur, evidently, only at compara-
tively long intervals, and each segment presumably gives rise to
a leaf. The first division in each segment is longitudinal and

X FILICINE^ LEPTOSPORANGIAT^ 323

perpendicular to its broad faces. Each of the six semi-segments
is then divided into an inner and an outer cell, and the latter
again by a longitudinal wall parallel to its inner and outer faces,
so that each original segment is divided into two inner cells
and four outer ones. From the inner cells the pith and vascular
bundles arise, from the outer ones the cortex and epidermis,
but after the first divisions there is great irregularity in the
succession of the cells. The young vascular bundles can be
traced nearly to the apex, and first appear as bundles of
procambium cells, which lower down unite and are joined by
others from the leaves and roots.

In (?. struthiopteris characteristic air-chambers are formed
in the young medulla at an early period. At certain points
the cells become longer and their contents more transparent.
These cells divide less rapidly than the surrounding tissue, and
large intercellular spaces are formed. The loose cells about
these form masses of trichomes, either hairs or scales, which
later dry up and leave a large empty space, which may or may
not communicate with the exterior through the foliar gaps.

In Onoclea struthiopteris, as in most leptosporangiate Ferns,
the outer cortical cells become changed into sclerenchyma.
In (?. struthiopteris the sclerenchyma forms several hypodermal
layers, distinctly separated from the inner cortical parenchyma.
These sclerenchyma cells are much elongated ; their lateral
walls are somewhat uneven, and in their younger stages swell
up more strongly under the action of potasisic hydrate than do
the cortical cells. Their walls become thick, are first pale
yellow, and later a dark reddish brown. The walls are very
markedly striate, and the central lamella distinct. Deep pits
extend down to the latter.

The bundles in the stems of the Polypodiaceae are very
uniform in structure. They are usually elliptical in section,
and the first tracheary tissue formed is a strand of small spiral
or reticulate tracheids at the foci of the bundle. From there
the formation of the very large scalariform ones, so characteristic
of the leptosporangiate Ferns, proceeds towards the centre of
the bundle, where the last -formed ones are situated. The
young tracheids have thin walls and abundant protoplasm, but
as the wall thickens, the contents gradually disappear, and
finally no living protoplasm remains in them. Faint elongated
transverse pits become evident, and the spaces between these

324

MOSSES AND FERNS

rapidly thicken at the expense of the cell contents until all the
protoplasm is used up. The thickened bars between the pits
give the characteristic ladder-like appearance to the older
tracheid (Fig. 163, B). In cross-section these bars are nearly
rhomboidal, and give the familiar beaded appearance to 'sections
of the tracheid wall.

Sieve -tubes of very characteristic form are found in the
bundles of all the Poly pod iaceae. In O. struthiopteris they

Fig. 163. — A, Vascular bundle from the rhizome of Pteris aguilina (L.) ; en^ endodermU ; s, j, sievt-
tubes : /, /, vessels (after Atkinson) ; B, longitudinal section of two large scalariform tracheae of
the same species (after Atkinson) ; C, part of a sieve-tube of Onaclea struthiopteris^ x 375.

occupy an irregular area at each end of the bundle. Their
differentiation begins shortly after that of the lai^e scalariform
tracheids, and in some respects resembles it. The procambium
cells from which they arise are uniform in diameter, and have
squarer ends than the young tracheids. Their contents are
more colourless and finely granular than those of the tracheids,
and the nucleus not so evident. Whether the subsequent
division of the nucleus takes place before the thickening of the
wall begins was not determined. The formation of the sieve-
plates begins by transverse thickened bars on the lateral walls.

X FILICINE.^ LEPTOSPORANGIAT^ 325

less regular than in the tracheids, and the bars more or less
anastomosing so as to enclose thin areas, the sieve-plates (Fig.
163, C). These occur all over the lateral walls, as well as the
transverse ones. While it could not be positively shown, it is
extremely probable that the pores, afterwards formed, penetrate
completely the thin membrane of the sieve-plates, and throw
the adjacent sieve-tubes into conpmunication.

The Leaf

While the leaf in a few of the Leptosporangiatae is simple,
in much the larger number it is compound, either dichotomously
branched {Adianium pedaium) or more commonly pinnately
divided. Owing to the great irregularity of the divisions and
slow formation of new segments in the stem apex, it is
exceedingly difficult to determine positively whether each
segment of the stem apex produces a leaf, but this seems
probable. The leaf appears as a blunt conical emergence,
whose apex is occupied by a single large apical cell, which in
nearly all forms examined is wedge-shaped and forms two rows
of segments. As the leaf grows it assumes the form of a
flattened cone with a broad base, more convex on the outer
side, and very soon showing the circinate vernation. The
petiole grows much more rapidly than the lamina, which remains
small until the close of the season before which it unfolds. In
most species of colder climates the development of the leaves
is very slow, and may occupy three or four years. The last
stage of growth consists merely in an expansion of the leaf,
with comparatively little cell division. This latter phase of'
growth often goes on with great rapidity, in strong contrast to
the excessively slow growth during the early stages.

The first wall in the young segment of the apical cell
divides it into an inner and an outer cell, and the latter then
divides into two by a longitudinal wall, and each of the latter
into two more by a transverse wall. Of these five cells, the
inner ones, in the lamina of the leaf, produce the rachis, the
outer ones the lamina itself. The outer cells of the segments
form the pinnae. Soon after the separation into lamina and
petiole, the development of pinnae begins in those Ferns which,
like 0, siruthiopteriSy have pinnate leaves (Fig. 162, D). Their
formation is strictly monopodial, and begins by an increase in

326 MOSSES AND FERNS chap.

growth in the outer cells of the young segment, which thus form
a lobe. The marginal cells divide rapidly by longitudinal walls,
so that at first the young pinna does not grow from a single
apical cell, but sometimes two of the division walls intersect and
an apical cell is formed. Whether this always happens could
not be absolutely determined. As each pinna corresponds to
a segment of the apical cell of the leaf, it follows that they
alternate with each other on opposite sides of the rachis.
Where these grow from an apical cell, the divisions follow
those in the apex of the leaf. From the inner cells of the
segments the rachis of the pinna is developed. The midrib of
each lobe of the pinna bears the same relation to it that the
rachis does to the pinna itself. The secondary veins arise in
acropetal succession, and at first form a strand of procambium
reaching from the midrib to the margin. Where dichotomy of
the veins occurs, as it so frequently does in their ends, this is
connected with a dichotomy of the marginal group of meriste-
matic cells.^ * Each marginal cell, like the segment of the apical
cell of the leaf, divides into an inner and an outer cell. The
latter then divides longitudinally, and the dichotomy is thus
inaugurated. These secondary marginal cells now repeat the
same divisions, and the two diverging rows of inner cells form
the beginning of the young veins.

Except the smallest veins, which are collateral, the bundles
are typically concentric, and differ only in minor particulars
from those in the stem. The ground tissue of the petiole shows
much the same structure as that of the rhizome in most Ferns,
and usually develops several layers of hypodermal scler-
enchymas. In the lamina, the cells of the ground tissue, as the
leaf expands, separate and form large intercellular spaces
between them. The cells are in many places connected by
prolongations or protrusions of the wall. On the upper side, in
cases where no stomata are developed, an imperfect palisade
parenchyma may form, but in none of the forms examined by
me was it nearly so distinct as in Angiopteris. The fully-
developed epidermal cells are very sinuous in outline, and
always contain numerous chloroplasts.

In Onoclea struthiopteris stomata are developed only upon
the lower side of the lamina, but sometimes these also are found
upon the upper surface as well. Usually, but not always, tlie

^ Sadebeck (6), p. 270.

FILICINEAl leptosporangiata-:

327

formation of the young stoma is preceded by the formation of
a preliminary cell (Fig. 164, v\ horse-shoe shaped, and cutting
off a small cell from one corner of an epidermal cell. A similar
wall forms within this small cell, parallel to the first one (Fig.
164, B, st\ and the cell thus separated is the stoma mother cell.
A longitudinal wall next divides this, and then splits in the
middle to form the pore of the stoma (Fig. 164, C). This when
complete is exactly in structure like that of other vascular

Fig. 164. — Adiantum emarginatnm (Bory). Development of the stomata, X 525 ; r, accessory cell ;

sty stoma mother cell.

plants, and like them communicates with the air-spaces of the
mesophyll. The accessory cell enlarges very much with the
expansion of the leaf, and its walls have the same sinuous out-
line that the other epidermal cells exhibit. A curious variation
of the ordinary form is seen in Aneitnia} where the mother cell
of the stoma is cut out by a perfectly circular wall, very much
like the funnel-shaped one in the antheridium, and the stoma is
apparently free in the centre of an epidermal cell. It seems
that this also occurs in Polypodium lingua?

^ De Bary (3), p. 42. '^ De liar)-, Lc.

328 MOSSES AND FERNS chap.

Most of the Leptosporangiatae are characterised by numer-
ous epidermal outgrowths, either hairs or scales. These are
especially abundant upon the younger parts, and are largely
protective. The hairs are either simple or glandular ones. In
the latter case the gland is usually a terminal, pear-shaped cell,
which secretes mucilaginous matter, or less frequently {Onodea
struthiopteris) this secretion may be resinous. In the common
Californian " gold-back " Fern, Gytnnogramnte triangularis^ the
yellow powder upon the back of the leaf is a waxy secretion,
derived from epidermal hairs. Of similar nature are the lai^e
chaffy scales (paleae) which occur in such numbers upon the
bases of the petioles of so many Ferns. This development of
hairs, however, is most marked in the large tree- Ferns, Dicksonia,
Cibotium^ etc., where the young leaves are completely buried in
a thick mass of brown wool-like hairs, which are sometimes
utilised as a substitute for wool in stuffing mattresses, etc.

The Root

The roots arise in large numbers in most Ferns, and
apparently bear no definite relation to the leaves. The primary
ones are first visible very near the apex of the stem (Fig. 162,
A, r), and Van Tieghem,^ who has made a very exhaustive study
of the subject, states that they always arise from an endodermal
cell. This divides into a basal cell and a terminal one, and by
the former the young root is directly connected with the xylem
of the stem bundle. In the outer cell the three walls defining
the pyramidal apical cell now arise, and the latter at once
begins its characteristic divisions.

The segmentation in the apex of the roots of the Lepto-
sporangiatae is exceedingly regular. Corresponding to each
set of lateral segments an outer segment forms as well. Van
Tieghem ^ does not apparently recognise the root-cap as distinct
from the epidermis, but all other observers consider the root-
cap as a distinct structure. The first division wall in the lateral
segments is the sextant wall, which is perpendicular to the broad
faces of the segment and curves somewhat so as to strike one of
the lateral walls a little above the base, and thus makes the two
sextant cells of unequal size (Fig. 165, C). The next wall is
transverse and separates an inner from an outer cell, and with

^ Van Tieghem (5). ' Van Tieghem, U,

FILICINE^ LEPTOSPORANGIATyE

329

this divides the plerome from the cortex. After this in the
outer of the primary cells there is a separation of an outer from
an inner cell, the former giving rise either directly or by a
subsequent division to a single layer of cells upon the outside
of the root, which is usually regarded as the epidermis, and the
inner cells form the cortex. The inner layer of the cortex,
which can be traced back almost to the summit, is the
endodermis, and its radial walls are peculiarly folded.

Fig. 165. — Adiantum etnarginatum (Bory). A, Longitudinal ; B-E, a series of transverse sections
of the root, x 200 ; ^, apical cell : f-j, sextant walls ; r#f, endodermis.

According to Strasburger,^ in Pteris Cretica the cap cells
divide only by perpendicular walls, and the older layers of the
cap remain but one cell in thickness. Van Tieghem ^ states,
and I have verified this in Adiantum emarginatum and
Polypodium falcaiuvty that with the exception of the first-
formed cap cell (or " epidermal segment," to use his termino-
logy), there is, in the central part, always a doubling of the cells

* Strasburger (10).

Van Tieghem (5), p. 532.

330 MOSSES AND FERNS chap.

by periclinal walls, so that each layer of the older root-cap is
normally double, except sometimes at the extreme edge.

There is very little displacement of the cells for a long
time, and cross-sections of the root, made some distance below
the summit, still show the limits of the original sextant walls^
which form six radiating lines with periclinal walls arranged
with great regularity. In the centre the divisions proceed with
great rapidity, and the plerome soon shows the elongated
narrow procambium cells. In the centre are four much larger
cells, which develop later into tracheids, and three of these can
be traced back to the central cells of the three larger sextants
(Fig. 165, D) ; the fourth arises from the inner cell of one of
the smaller ones. This central group of cells marks the
position of the plate of tracheary tissue, found later in the
root. By this time the parts of the complete root are all in-
dicated. The bundle is bounded externally by the endodermis,
whose cells are much elongated transversely, and clearly dis-
tinguishable from the pericambium (pericycle), which consists of
one or two rows of cells. Inside this is the mass of procambium
cells, the large tracheids of the central part of the xylem being
very evident. The masses of procambial cells on either side of
this central line of cells constitute the young phloem.

The primary tracheids (proto-xylem) arise simultaneously at
the foci of the section, and consist of a single line of narrow
pointed tracheids, with fine spiral markings, very closely set at
fifst, but later pulled apart somewhat with the increase in length
of the root. These are formed a long time before any other
permanent tissue elements can be distinguished. Around these
primary tracheids are formed a group of similar ones, and from
here the formation proceeds towards the central group of large
tracheids, which are the last to have their walls thickened and
lignified. The large secondary tracheids are scalariform, like
those of the stem. The cells of the pericycle remain nearly
unchanged, but in the two phloem masses, according to
Poirault,^ sieve-tubes are always present. These tubes are of
two types, with horizontal transverse walls, or inclined ones.
The perforations in the sieve-plates were demonstrated, and
lateral perforations, either isolated or in groups, also occur.
His statement that the sieve -tubes have no nuclei requires
further proof. The walls of the sieve-tubes are of cellulose,

1 Poirault (i).

X FILICINE^ LEPTOSPORANGIATAi: 331

but in the sieve-plates callus is found. The rest of the phloem
is composed of conducting cells, with thin walls and oblique
septa. The endodermis becomes dark -coloured and its walls
lignified, and when the root dries the vascular cylinder often
becomes separated from the ground tissue by the transverse
splitting of the endodermal cells.

The secondary roots arise in regular succession in two
lines, corresponding to the ends of the xylem plate in the
diarch bundle. They themselves generally branch further, and
thus very extensive root systems are formed. The origin of
the lateral roots of the Ferns has been exhaustively studied by
Lachmann,^ but their position seems to be of very little import-
ance systematically, and except in a few cases like Osmunday
where two roots regularly arise for each leaf, there is little
relation between roots and leaves. In creeping rhizomes they
arise either mainly from the ventral side or from all parts
indiflferently. As yet the only forms in which complete
absence of roots is known among the Leptosporangiatae are
Scdvinia^ species of TrichomaneSy and Stromatopteris^ one of
the Gleicheniaceae. In all of these, however, there are
substitutes either in the form of modified leaves {Salvinia) or
root-like rhizomes.

The formation of buds from the roots, such as occur in
OphioglossufHy have been also observed in some Leptosporan-
giatae. This was first discovered by Sachs in Platycerium
Wallichiiy and later described by Rostowzew,* and Lachmann *
also describes it in Anisogoniuni Seramporense. In all these
cases the apex of the root appears to become transformed
directly into the apex of the bud.

TJie Sporangium

The development of the sporangium of all the Leptosporan-
giatae is much the same, but the position of the sporangia, and the
character of the indusium when present, varies much, and will
be discussed later as the different families are treated separately.

In the Polypodiaceae the sporangia, as is well known, arise
usually in groups (sori) upon the backs of leaves that differ
but little from the ordinary ones. Sometimes, however, eg.
Onocleay they are very different, the sporangia being produced

^ LachmaDn (7). ' Poirault (2), p. 147. ' Rostowzew ( 1 ). * Lachmann (7).

332

MOSSES AND FERNS

CHAP.

in great numbers, and the lamina of the leaf much contracted.
One of the simplest cases is seen in Polypodiunt, Here the
sporangia develop late upon ordinary leaves, and form scattered
round sori, bearing, however, a definite relation to the veins —
in this case forming above the free end of one of the small
veins. Where there are special sporophylls, the development
of the sporangia begins before the leaves begin to unfold.

Fig. i66. — PolyPodium ftdcatum (Kellogg). A, Cros»-secdon of a sterile leaf, cutting across one of
the smaller veins, x 260 ; sU section of a stoma ; B, similar section of a sporophyll, showing the
position of the sorus above the vein, X85.

In Polypodium (Fig. 167) the first evidence of the formation
of sporangia is a series of minute depressions upon the lower
side of the leaf, much as occurs in Angiopteris, The bottom of
this depression is occupied by a low elevation, the placenta, and
upon this the sporangia form in an analogous way, but are not
all developed at the same time, .so that a single sorus may

FILICINEAl LEPTOSPORANGIAT.iC

III

contain nearly all stages of development. The sporangium
here can be readily traced back to a single epidermal cell.

The sporangial cell protrudes until it is nearly hemi-
spherical, when it is cut off by a wall level with the surface of
the placenta. This basal cell takes no further part in the
development of the sporangium, and after a time becomes
indistinguishable. The outer cell now divides by a wall,
occasionally transverse, but much more commonly strongly
inclined (Fig. 167, A), and striking the basal wall. This is

Fig. it-j.—Pofypodiunt falcaium (Kellogg). Development of the sporangium. A-E, from living
specimens; F, G, microtome sections; A, B, C, optical sections; D, £, the same sporangium,
showing respectively the surface ce^s and central optical section ; /, /, tapetum. A-E, X400 : F,
G, xaoo.

now followed by two others, also inclined, and meeting so as to
enclose a pyramidal apical cell, from which a varying number
of lateral segments are cut off. These form three rows,
corresponding to the three rows of cells found in the stalk,
which is not sharply separated from the capsule, as stated by
Goebel,^ and formed from the lower of two primary cells, but
is merged gradually into the capsule, and owes its three-rowed
form to a primary and not a secondary division. The upper
part of the young sporangium enlarges, so that it becomes

* Goebel(io), p. 218.

334 MOSSES AND FERNS chap.

pear-shaped (Fig. 167, B), and a periclinal wall is then formed
in the apical cell. The cells of the stalk undergo no longi-
tudinal divisions, and it remains permanently composed of
three rows.

Kiindig^ first called attention to the real state of aflfairs,
and since, C. Miiller ^ has investigated the matter further. The
central tetrahedral cell of the young sporangium (archesporium)
has cut off from it, by periclinal walls, the primary tapetal cells
(/), and in the meantime the wall of the capsule forms repeated
radial divisions but no periclinal ones, and, unlike that of the
eusporangiate Ferns, always remains single-layered. A surface
view of the sporangium at this stage shows the last-formed
lateral segment to still retain its triangular form, and the cell
divisions in it are very regular. After two or three transverse
divisions, a median vertical wall follows, and in each of the
resulting cells a transverse wall. Of the two upper cells, one,
according to Muller,* remains undivided, the other divides again
by a vertical wall, and the inner of the two cells thus formed
by further transverse divisions forms the stomium or mouth of
the sporangium.

The cells of the young sporangium contain but little
granular contents, and the divisions are very evident. As soon
as the archesporium is formed its contents begin to assume a
more granular appearance, and become more highly refractive
than those of the surrounding cells. The contrast between the
archesporial cells and those of the wall increases as the sporan-
gium grows older.

The first division in the central cell begins soon after the
separation of the primary tapetal cells. The direction of this
first wall is usually transverse, but may be more or less
inclined, or even vertical. In each of these cells a wall is
formed at right angles to the first-formed, and the quadrant
cells are again divided into equal octants. Each of these eight
cells divides once more (Fig. 167, G), and the sixteen spore
mother cells, found in most Ferns, are complete. In Onodea
struthiopteris I found twelve as the ordinary number, but at what
point the division is suppressed was not made out. During the
division of the central cells the tapetal cells also divide, first
by radial walls only, but later by one set of periclinal walls.
This doubling of the tapetum, while it occurs in the majority

» KUndig(i). 2 MlUler, C. (2). » MUller, Lc,

X FILICINE^ LEPTOSPORANGIAl^E 335

of Polypodiaceae, does not seem to be universal.^ The cells of
both sporogenous cells and tapetum have dense granular
cytoplasm, and large nuclei. Soon after the divisions in the
sporogenous complex are completed, the walls of the tapetal
cells become broken down, and their contents dispersed
through the large central cavity. The sporangium continues
to enlarge rapidly after this, and the spore mother cells, still
united, float in a large cavity, which in the living sporangium
seems to be filled with a structureless mucilaginous fluid, but
when fixed and stained is seen to contain the unchanged nuclei
of the tapetum, as well as its cytoplasmic contents. Gradually
the connection between the sporogenous cells is lost, and the
isolated cells, each surrounded by a very delicate membrane,
float in the large central cavity. Here they divide into four
cells, as usual, and the division may be simultaneous, resulting
in tetrahedral spores, or successive {Onoclea\ in which case
bilateral spores are formed. Strasburger* states that during
the division of the spores in Osmunda there is a reduction of
the chromosomes to one-half their original number, but whether
this also occurs in the other Ferns must be left undecided at
present. Stained microtome sections of sporangia during the
formation of the spores show that the spore mother cells, and
afterwards the spores themselves, are embedded in a granular
matter, evidently the product of the disorganised tapetum, and
that the nuclei of the latter are collected about them, evidently
intimately associated with the growth of the young spores, and
in the later stages with the formation of the perinium. The
latter is rarely smooth, but shows spines, ridges, and folds of
characteristic form in different species.

When chlorophyll is present in the ripe spore it only arises
at a late period. In Onoclea struthiopterisy about the time that
the perinium begins to form, numerous small colourless granules
appear near the nucleus, and with the ripening of the spore
these increase rapidly in size and number, and an examination
shows that the increase in number is the result of division.
These are young plastids, and as they enlarge chlorophyll is
formed in them, and they become very much crowded, so that
the green colour of the ripe spore is very pronounced.

The further history of the sporangium wall is somewhat
complicated. The stomium, as we have seen, arises from a

* Goebel (10), p. 218. ^ Strasburger (12), p. 293.

336

MOSSES AND FERNS

CHAP.

special cell of the last-formed lateral segment. The segment
on the opposite side (next older but one) shows a quite similar
arrangement of cells, and, according to Miiller,^ the cell corre-
sponding to the stomium by two transverse walls forms the
first segment of the annulus. The cells immediately below also
divide similarly, and give rise to a second section. The rest of
the annulus arises from the upper or cap segment of the
sporangium wall, and extends from the stomium over the top
of the sporangium, and joins the part of the annulus upon the

other side. The walls of
all the cells are at first
alike, but those of the
annulus begin to thicken,
this being confined to
their inner and radial
walls, the outer walls re-
maining thin. In most
species the cells of the
annulus are the same for
the whole extent, but in
P oly podium falcatum (Fig.
1 68), which is figured
here, the cells of the an-
nulus immediately above
the stomium are larger
and thinner-walled. The
stomium cells are more
extended laterally than
the other cells of the an-
nulus, and between them
the sporangium opens by
a wide horizontal cleft
Atkinson "^ describes the process thus for the Polypodiaceae.
" While the opening of the stomium between the lip cells is
aided by their peculiar form, it seems possible that at maturity
the line of union is less firm than between the other cells.
The fissure once started proceeds across the lateral walls of
the sporangium, usually in a straight line, thus splitting in
half the cells of the middle row, their frailty favouring this.
The drying of the annulus brings about the unequal tension
» MiiUer, C. (2). « Atkinson (3), p. 68.

Fig. 168.— Surface view of a nearly ripe sporangium of
Polypodium falcatum, X 175 ; */, stomium ; r,
annulus.

X FILICINEyE LEPTOSPORANGIATjE 337

of its cell walls. During this process it slowly straightens,
carrying between the distal portion of the lateral walls of the
sporangium, which remain attached to the free extremity, the
greater part of the spores. When straight, it continues to
evert, and this usually proceeds until the two ends of the
annulus nearly or quite meet, when with a sudden snap it
throws the spores violently away and returns to nearly its
normal position."

Paraphyses, in the form of pointed hairs, often with a
glandular terminal cell, sometimes occur with the sporangia.
These in some Ferns, e.g, Aspidium filix-mas^ are direct
outgrowths of the sporangium itself.

CHAPTER XI

CLASSIFICATION OF THE HOMOSPOROUS LEPTOSPORANGIATwt

Fam, L Osmundacece^

The Osmundaceae, which in many respects form a transition
from the eusporangiate to the leptosporangiate Filicineae, are
represented by two genera, Todea^ with four species, mostly
confined to Australasia, one species only being found in South
Africa ; Osfnunda^ with six species, belonging mainly to the
temperate and warm temperate regions of the northern
hemisphere. The widely distributed species Q, regcdis is
found also in South Africa, but otherwise they belong
exclusively to the northern hemisphere. Osmunda has the
large sporangia borne on very much modified sporophylls,
which recall strongly those of Botrychium or Helminthostachys ;
Todea^ while its sporangia are like those of Osmunda^ has
them borne upon the backs of ordinary leaves.

The development of the gametophyte is completely known
in Osmunda^ and somewhat less perfectly in Todea^ which
does not, however, seem to differ essentially from Osmunda.
In the latter there is considerable difference in the species
examined. In all of them the spores contain chlorophyll
at 'maturity, and quickly lose their power of germination.
Sown as soon as ripe, they germinate very promptly, and
the first division of the spore often takes place within
twenty-four hours. The early stages show great variation,
even in the same species, and these seem to be often quite
independent of external conditions. The ungerminated spore

1 Hooker and Baker (i). « Kny (5) ; Campbell (12). » Luersscn (3).

CHAP. XI THE HOMOSPOROUS LEPTOSPORANGIAT^

339

has an exceedingly delicate endospore, which is difficult to
demonstrate, but after the exospore bursts along the three
ventral ridges, and the endospore is exposed, it becomes
very evident.

The first division takes place after the spore has elongated
slightly, and is usually transverse, separating the small root-hair

5p D

Fig. 169. — Osmunda Claytoniana (L.X A, Ungerminated spore ; i, ventral surface ; 3, optical
section, x 550 ; B, germinating spores, x 275 ; r, primary rhixoid ; C-E, older stages, X 275 ; */,
spore membrane ; x, apical cell.

from the large prothallial cell (Fig. 169, B). The young root-
hair contains chlorophyll, but not so much as the larger cell.
As germination proceeds the chloroplasts separate and increase
in size. They are often arranged in lines extending from the
large nucleus to the periphery of the cell. As a general thing.

340

MOSSES AND FERNS

the growth of the prothalHum is exactly opposite to that of
the first rhizoid (bi-polar germination), and Kny ^ lays a good
deal of stress upon this, as distinguishing Osniunda from the
Polypodiaceae ; but it is not at all uncommon for O. Claytoniana^
especially, to have the axis of growth of the rhizoid almost or
quite at right angles to that of the prothalHum, exactly as in
the Polypodiaceae. Where the germination is truly bi-polar
the exospore is pushed up with the growing prothalHum, and
appears like a cap at its apex, but if the root-hair is lateral,
the exospore remains at the base.

In O. Claytoniana there are usually several transverse walls

Fig. 170. — Osmutida cinnantomea (L.). A, Young prothallia ; B, an older prothalliuin, X260.

formed before any longitudinal ones, but in O, cinnaviomea
and O, regalis it is quite common to have the first
transverse wall followed by a longitudinal wall in each cell, so
that the four primary cells are arranged quadrant-wise (Fig.
170, A, c). Rarely the first wall in the prothallial cell is
longitudinal, as is often the case in Equisetum^ and sometimes
the first divisions are in three planes, so that a cell mass is
formed at once, as so often occurs in the Marattiaceae. Where
a filamentous protonema is formed, a two-sided apical cell is
soon established in exactly the same way as in Onoclea, Where

1 Kny (5). p. 12.

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 341

the four quadrant cells are formed, one of the terminal ones
becomes at once the apical cell.

As soon as the apical cell is established, growth proceeds
as in OnocleUy and a heart-shaped prothallium is formed. One
difference, however, may be noted. Each segment cut off from
the apical cell divides first by a transverse wall into an inner
and an outer cell, but the inner cell from the first undergoes
divisions by horizontal walls, so that a central midrib is formed,
very much as in Metzgeria^ and the prothallium becomes more
elongated than is common in the Polypodiaceae. The single
two-sided apical cell persists for a long time, but is finally
replaced either by a single cell, much like that of Pellia
epiphylla^ or more commonly by a series of marginal cells, as
in the Marattiaceae or Polypodiaceae. The subsequent growth
of the prothallium is the same as in those forms, but no
definite relation could be made out between the archegonia
and the segments of the initial cells. Among the Hepaticae
Dendroceros oflers almost an exact analogy in the form of
the apical cells and the divisions of the segments.

According to Luerssen,^ in Todea a distinct apical cell is
often wanting, and the growth throughout is due to the activity
of several similar initials. His figures, however, hardly bear
out his statement, and further information is desirable on this
point.

As the prothallia grow older the midrib becomes conspicu-
ous, and projects strongly from the ventral surface. In O,
cinnamomea and O, regalis even at maturity it is very little
broader where the archegonia are formed, but in O. Claytoniana
it forms a cushion in front, much like that of Marattia or the
Polypodiaceae, and in this respect, as well as the form of the
apical cells, seems to approach the latter. In this species the
prothallium is lighter coloured, and the root-hairs not so dark,
while in its dark green colour and fleshy texture O, cinnamomea
recalls Anthoceros Icevis or Marattia.

Where a cell mass is formed at first, this condition is
temporary, and an apical cell is established which gives rise to
the ordinary flat prothallium. The small male prothallia, which
are formed in large numbers, exhibit various irregularities, and
quite commonly do not show any definite apical growth, and in
0, Claytoniana especially often branch irregularly, or in some

* Luerssen (3).

342

MOSSES AND FERNS

CHAP.

cases there is a true dichotomy (Fig. 171, A). Slender
filamentous prothallia are especially common in this species
(Fig. 172, C), and recall somewhat those of some species of
Trichomanes.

The prothallia of the Osmundaceae often form adventitious
buds, much like those of the Marattiaceae. These secondary

Fig. xyz.— a, Apex of a young prothalUum of O, Ciaytonia$u», with two similar initials, jr, jr, X560;
B, longitudinal section of an advanced prothallium of O. cinstamomeat X26o; C, horicoatal
section of a similar one, showing two initials, X 260.

prothallia (Fig. 172, B) generally arise from the margin, but
may be produced from the ventral surface. An apical cell is
usually early established, and the subsequent growth is closely
like that of the primary one.

The prothallia are long lived if they remain unfertilised, and
Goebel ^ states that in O, regalis they may reach a length of four

* Goebel (16), p. 199.

THE HOMOSPOROUS LEPTOSPORANGIAT^

343

centimetres. He also records a genuine dichotomy of the older
prothallia of this species.

Tlu Antheridium

Under favourable circumstances the first antheridia appear
after about a month in O, Claytoniana^ and continue to form for

Fig. 172.— a, Prothaliium of O. Claytoniana^ about two months old, x about 30 ; B, base of an
older prothaiUuni of the same species with a secondary prothaliium (^) growing from it, X 80 ;
6 , antheridia ; C, small branching male prothaliium of the same species, X 75.

a year or more. In O. cinnamomea they first appeared about
two weeks later. While they are almost always present upon
the large female prothallia,^ numerous exclusively male plants
are always met with. These latter are usually irregular in form,
and even filamentous, especially when crowded. Upon the
latter the antheridia are either terminal or marginal; in the
flattened prothallia they occur mainly upon the margin and

* Luerssen {I.e. p. 449) states that they are often absent from very vigorous
prothallia.

344

MOSSES AND FERNS

CHAP.

lower surface of the wings. The development corresponds
closely in all forms that have been examined, and differs
considerably from that of the Polypodiaceae.

The mother cell is cut off as usual, but the second wall is
not funnel-shaped, but plane and inclined, so that it strikes the
basal cell. In the larger of the two cells thus formed a vary-
ing number of divisions occur, cutting off a series of lateral
segments, much after the fashion of a three-sided apical cell.
The segments thus cut off form the basal part of the antheridium,
and when the number is large a pedicel may be formed. When
the full number of basal segments is complete, a dome-shaped

Fig. 173. — A-D, Development of the antheridium of O. cinttamomea^ in longitudinal secdoo,
X435 ; E, F, G, three surface views of a ripe antheridium of O. Ciayi0ma$ta -, £, from above,
the others from the side ; «, opercular cell, X425.

wall arises in the apical cell, as in the Polypodiaceae, and the
central cell has much the same form (Fig. 173, A). This has
no chlorophyll, and as usual the large distinct nucleus is
embedded in dense highly refractive cytoplasm. There are
next formed in the outer dome-shaped cell two or three walls,
running more or less obliquely over the apex ; either at the top
or at one side the last-formed wall encloses a small cell, which
is thrown off wh^n the antheridium opens (Fig. 173, o). This
opercular cell, both in form and position, recalls strongly that
found in the Marattiaceae.

The divisions in the central cell correspond closely to those

THE HOMOSPOROUS LEPTOSPORANGIAT^

345

in Onoclea, but the number of sperm cells is larger, being
usually lOO or more. The development is also the same, and
will not be entered into here.^ After the final division of the
sperm cells the nuclei remain slightly flattened in the plane of
division, as in the Hepaticae, and the mature spermatozoids
are coiled more flatly than in the Polypodiaceae. The free
spermatozoid recalls that of Marattia or Equisetum rather than

Fig. 174. — A, Ripe antheridium of O. Clayioniana^ just ready to open ; B, the same discharging tne
sperm cells, x6oo ; C, two spermatozoids, x 1200.

the Polypodiaceae. There are but about two complete coils,
and the hinder one relatively larger than in the latter forms.
In swimming there is peculiar undulating movement, suggestive
of the spermatozoid of Equisetum,

The Ardugoniuni

The archegonia are only borne upon the large heart-shaped
prothallia, and occupy the sides of the projecting midrib, where,

* For details see Campbell (12), p. 61.

346

MOSSES AND FERNS

CHAP

if the earlier ones are not fertilised, they may continue to form
indefinitely ; but no correspondence can be made out between
them and the initial cells, and while formed for the most part
in acropetal order, new ones may arise among the older ones.

The mother cell of the
archegonium is scarcely dis-
tinguishable from the neigh-
bouring cells, either in size
or contents, and cannot al-
ways be identified until after
the first transverse divisions.
The development is much as
in the other Ferns, but there
are some differences that may
be noted. The first trans-
verse division, as in these^
separates the cover cell from
the inner cell, and the latter
may divide into a basal and
central cell, but sometimes
this division is omitted, and
the basal cell is absent. The
cover cell divides by the usual
cross-walls into the four prim-
ary neck cells, which here all
develop alike, and the neck
remains straight. The com-
plete neck has about six tiers
of cells. The separation of
the neck and ventral canal
cells follows in the usual
manner, but occasionally the
former may be divided hy a
transverse cell wall (Fig. 175,
A), although ordinarily the
division is confined to the
nucleus. The neck cells have
small nuclei, and in the living state are almost transparent,
with little chlorophyll. Small glistening bodies, apparently
of albuminous nature, are often present, and are especially con-
spicuous in material fixed with chromic acid. Kny and Luers-

FiG. 175.— A, Young archegonium of O. citmamo-
mta^ with the neck canal ceil divided by a cell
wall ; B, a nearly ripe archegonium of the same
species, X595.

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 347

sen both speak of the quantity of starch in the axial row of
cells in O. regalisy but in neither O. cinnamomea nor O. Clay-
toniana was this noticeable. As the egg approaches maturity
the nucleus becomes large and distinct, and one or two nucleoli
are present. The chromosomes are not conspicuous, a con-
dition that we have seen before is not uncommon in the egg
nucleus.

A curious appearance was noted several times just before
the archegonium seemed about to open, and after the formation
of the ventral canal cell. This was the separation from the
upper part of the egg of a small body containing what looked
like a nucleus. Whether this is something analogous to the
" polar body " found in animal ova could not be determined.

When the archegonium opens, the four rows of cells bend
strongly outward, and frequently some of the terminal cells
become detached. A large receptive spot is present, and the
nucleus is smaller than in the younger egg, and contains more
chromatin, and usually but a single nucleolus.

Fertilisation

The horizontal position of the archegonia, as they project
from the sides of the midrib, makes it easier to follow the
entrance of the spermatozoid than is the case in most Ferns.
The spermatozoids collect about the mouth of the freshly-
opened archegonium, and soon one finds its way in. With the
ciliated end down, it revolves rapidly, not seeming to be much
impeded by the mucilage thrown out by the archegonium.
Suddenly, with a quick movement, quite unlike the slow worm-
like movement seen in most Ferns, it slips through the neck
into the central cavity, where its movement is resumed. After
about three or four minutes it disappears, and has presumably
penetrated the egg. Other spermatozoids may make their
way into the central cavity, but only one penetrates the ovunri.
The lower neck cells now approach, but not enough to prevent
the entrance of other spermatozoids. Within a few hours the
inner walls of the neck cells begin to show the brown colour
that indicates that fertilisation has been accomplished.

The egg quickly secretes a cellulose membrane, which
prevents the entrance of the other spermatozoids. The egg
nucleus moves towards the receptive spot at the time of

348

MOSSES AND FERNS

CHAP.

fertilisation, where the spermatozoid may be seen but little
altered in form. It almost at once comes into contact with
the female nucleus, and the two then move toward the centre
of the ovum. Here the spermatozoid gradually loses its coiled
form and contracts until it becomes oblong, and in close
contact with the egg nucleus, in some cases looking as if it
were actually within it. The process is a slow one, and in one
case twenty-four hours after the entrance of the spermatozoid
the two nuclei were still recognisable. Finally they are
completely fused, and a single nucleus, with usually, perhaps
always, two nucleoli is seen. No sign of a separation of the
chromosomes of the copulating nuclei was observed.

The Embryo

The first division of the ovum is the same with respect to
the archegonium as in Onoclea, ue. the basal wall is parallel

Fig. 176.— a, Vertical section of an eight-celled embryo of O. Ciayt<miatut^ X36ow Mediaa
' longitudinal section of an older embryo of the same species, X 960 ; C, two transTcrse sections of
a somewhat younger embryo of O, ciMttamcmea^ X 260 ; */, stem apex ; L, cotyledcm ; r, primary
root ; F, foot.

with its axis ; but the quadrant wall is also parallel with this
instead of transverse, although its position with reference to the
axis of the prothallium is the same ; so that the embryo-

THE HOMOSPOROUS LEPTOSPORANGIATA£

349

quadrants, and the organs derived from them, are situated like
those of the polypodiaceous embryo, with reference to the
prothallium, but not to the archegonium.

As in Onoclea the primary organs are established by the
first two walls, and the next divisions form octants, but there is
somewhat less regularity in the later divisions, in which respect
Osmunda is intermediate between the Polypodiaceae and the
Eusporangiatae. As in the former, the two epibasal quadrants
form stem and cotyledon, the hypobasal ones, root and foot.
At this stage the cells of the young embryo contain but little

Fig. 177. — Three sections of one embryo of O. cinnamomea in which the root (r) is especially well
marked, X260. Lettering as in the last

granular cytoplasm, and there are large vacuoles. As the
embryo grows older the granular cell contents increase in
quantity. The subsequent divisions follow very closely those
in the embryo of Onoclea, but are less regular, and the embryo
retains for a longer time its original nearly globular form.

The direction of growth of the cotyledon is determined in
part by the first walls in its primary octants. The outer
octant usually becomes at once its apical cell, and if its first
segment is formed on. the side next the octant wall, this throws
the axis of growth very much on to one side, so that the axis
of the leaf may be almost at right angles to the median line of

350

MOSSES AND FERNS

CHAP.

the embryo. Otherwise it nearly coincides with this. The
original three-sided apical cell persists for a long time, and it

Fig. 178.— a, Horizontal section of an advanced embryo of O. Claytoniana, passing throu^ the
cotyledon and foot, X 230 ; B, longitudinal section of the stem apex in a somewhat older embryo
of O. cimtamomea, X 460 ; C, transverse section of the apex of the primary root of the same,
X460.

could not be positively shown whether or not it was afterwards
replaced by a two-sided one. The further development of the

Fig. 179. — Transverse section of a prothallium of O. ClayUmiana^ showing the lateral position of the

embryo (rwX X75'

cotyledon' corresponds almost exactly with Onoclea, It does
not break through the calyptra until later, and m this respect

THE HOMOSPOROUS LEPTOSPORANGIAT^

351

shows its primitive character. The single vascular bundle of
the petiole approaches the collateral type, and is much like
that of the cotyledon of Marattia. Stomata of the usual form
occur on both sides of the lamina. The development of the
stem offers no peculiarities. The apical cell is of the tetra-
hedral form found in the mature sporophyte.

The root is bulky, and the apical cell relatively small, with
large segments, dividing less regularly than in OnocUay and on
the whole approaches most nearly to Botrychium. The form
of the apical cell is like that of Onoclea or Botrychiunty and is
interesting because in the later roots this is replaced by another
form, so that this would indicate that the three -sided form
found in so many cases is the primitive condition. The
vascular bundle is diarch.

The foot is very large, and
while formed originally from the
upper hypobasal quadrant, it en-
croaches more or less upon all
the others. Very early its cells
cease to show any regular order
in their divisions, and divide more
slowly than the other cells of the
embryo, so that they become de-
cidedly larger. The cells lose
much of their protoplasm as they
increase in size, and serve simply
as absorbent organs. They are

in close contact with the prothallial cells, and crowd upon them
until the foot penetrates deep into the prothalHum, whose cells
it partially destroys. It is upon the large development of the
foot, whose outer cells sometimes are extended into root-like
extension like those in AntfioceroSy that the young embryo is
maintained so long at the expense of the prothalHum.

Frequently more than one embryo begins to develop, and
sometimes a number of archegonia may be fertilised ; but no
cases were met with where more than one embryo came to
maturity, although it is quite possible that this may occur.

Fig. 1 80. — Young sporophyte of O. Clay-
tonianay still attached to the prothal-
Hum, x6.

352

MOSSES AND FERNS

CHAP.

The Mature Sporophyte

The growth of the stem in the mature sporophyte is only
known in 0. regalis} Here there is usually an apical cell of

the same type as that
found in the Ophioglos-
saceae or Polypodiaceae,
but Bower* states that
sometimes it is impossible
to refer the tissues to the
division of a single initial
cell, and that there are
probably in these cases
several initials. The
growth of the stem is
much like that in the
other Ferns described,
and the structure of the
older parts shows much
the same arrangement of
the tissues as that in
the typical Polypodiaceae.
The vascular bundles,
however, are very de-
cidedly collateral in struc-
ture. A cross-section of
the stem (Fig. i8i, B)
shows a circle of horse-
shoe shaped or wedge-
shaped bundles, with the
xylem directed inward
and bordering directly
upon the pith. Between
the bundles are layers of
parenchyma (medullar>-
rays), and the phloem
forms a continuous band
outside the woody
bundles and bounded externally by the endodermis. The
ground tissue is mainly composed of dark sclerenchyma*

^ Bower ( 1 1). * Bower, /.r.

Fig. 181.— Upper port of a sporophyll of O. CUiytoniana^
X 9 ; </, sporangia ; B, section of the rhlEOuie of O,
regalis (L.X showing the arrangement of the vascular
bundles, X 4 (after De Bary).

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 353

through which the leaf-traces pass from the axial bundles to
the leaves. Each leaf-trace is surrounded by a sheath of
colourless cells.

The origin of the leaves is the same as in the Polypodiaceae,
but the young leaf grows from a three-sided apical cell much
like the stem,^ and the young leaf is more conical than there.
In the very young leaf, according to Bower, one side of the
apical cell is always directed toward the stem apex, and never
one of the angles. In the presence of a three -sided apical
cell, as well as its more cylindrical form, there is an approach
to Botrychium, The further development of the leaf is like
that of the pinnate leaves of the Marattiaceae or Polypodiaceae,
with which they agree also in the strongly circinate vernation.
The leaves are always pinnately divided, and are similar in all
the forms, and the type of venation is the same. While in all
species of Osmunda and in Todea Barbara^ the structure of the
leaf is quite like that of the Polypodiaceae, the other species of
Todea {Leptopteris) have the lamina of the leaf reduced to two
or three layers of cells, and there are no stomata. The
texture of the leaves in these forms is filmy, like that of
Hymenophyllum,

The petiole is traversed by a single large vascular bundle,
which in section is crescent-shaped and in structure concentric,
with the elements like those of the Polypodiaceae, but the
endodermis is not so clearly differentiated, and close to the
inner side of the bundle are numerous mucilage cells, recalling
the tannin ducts of Angiopteris. A further point of resem-
blance to the Marattiaceae is the presence of stipular wings at
the base of the petiole. The chaffy scales (paleae) so common
in the Polypodiaceae are quite wanting, but hairs are developed,
often in great numbers. Thus in O. cinnamomea the young
leaves are covered completely with a felted mass of hairs,
recalling those in some of the Cyatheaceae. Some of these are
glandular. The sterile leaves and sporophylls are either very
much alike, as in Todea^ or the sporophylls may be very
different. An extreme case is seen in O, cinnamomea^ where
the whole sporophyll is devoted to the development of
sporangia. In this species, as well as O. Claytoniana^ the
sporophylls develop first and form a group in the centre of a
circle of sterile leaves. In O, cinnamomea the sporophylls

* Bower (11), p. 332; Klein (2), p. 647.
2 A

354

MOSSES AND FERNS

develop no mesophyll, and die as soon as the spores are
scattered.

The Roots

The roots of the mature sporophyte differ very markedly
from those of the other Leptosporangiatae, and have been the
subject of numerous investigations, but there still is a good
deal of diversity of opinion as to their exact method of grow-th.
Bower ^ states that in O, regalis there may be a single apical

Fig. 182.— a, Longitudinal section through the root apex of O. cinnantointa; t, young tracfaeads,
X aoo ; B, cross-section of root apex of O. ClaytoMtafUL, x 200.

cell, such as exists in the first root of O, Claytoniana and O.
cinnamomea, but that it never shows the regular segmentation
of the typical leptosporangiate root, and it may be replaced by
two or three similar initials. In Todea barbara he found four
similar initials, and in no case a single one, although Van
Tieghem and Douliot ^ ascribe to this species a single three-
sided apical cell.^

Osmunda cinnamomea (Fig. 182, A) shows a single ver>'

* Bower (ii), pp. 310, 314. ^ Van Tieghem and Douliot (5), p. 378.

' Lachmann (i) asserts, however, that he found a group of initials such as Bower
describes.

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 355

large initial, more or less triangular in form when seen in
profile, but with the point sometimes truncate- Transverse
sections show that it is really a four-sided pyramid. The
young segments are very large, and it is possible that these
may sometimes assume the rdle of initials. Owing to the
slowness and irregularity of cell division it is difficult to trace
the limits of the segments beyond the youngest ones. They
usually form a spiral, but cases were sometimes encountered
where the segments were apparently cut off in pairs from
opposite sides of the initial cell. The root-cap arises in part
from special segments cut off from the outer face of the apical
cell, but also in part from the outer cells of the lateral segments,
as in the Eusporangiatae. The separation of the tissue system

Fig. 183. — OstHunda rtgalis (L,). A, Section of young sporophyll passing through three ver>'
young sporangia ; B, longitudinal section of an older sporangium ; /, the tapetum, X 335 (after
BowerX

follows much as in Botrychium, The plerome cylinder is large
and oval in section, but with poorly-defined limits, and it is
not possible to state positively whether it owes its origin
exclusively to the innermost cells of the segments. The large
central tracheae, as in Adiantum, afe very early distinguishable.
O. Claytoniana agrees on the whole with O. cinnamomea^ but
the divisions are much more regular, and it approaches nearer
the typical leptospofangiate type, both in the arrangement of
the young tissues and the structure of the fully -developed
vascular bundle, which closely resembles that of the Polypodi-
aceae, and differs from the investigated species of Osmunda and
Todea in the better development of the endodermis, and in
having the pericycle of but one or two layers.

356

MOSSES AND FERNS

CHAP.

The roots arise regularly, two at the base of each leaf,^
and their bundles connect with those of the stem near the
bottom of the elongated foliar gap in its vascular cylinder.

The Sporangia

The sporangia in Osmunda are produced upon sporophylls

that closely resemble those
of Botrychium or Helmintho-
stachySy but in Todea they occur
upon the backs of the leaves,
as in most Ferns. In structure
and development they are
intermediate between the true
leptosporangiate type and the
eusporangiate. So far as they
have been investigated they all
correspond very closely. The
origin of the sporangia is al-
most identical with that in
Botrychium^ and more than
one cell may take part in their
formation.^ Bower says : " In
all cases, however, one cell
distinctly takes the lead, and
this we may call the initial
cell (Fig. 183, A); but the
arrangement of its division
walls does not, as in the true
leptosporangiate Ferns, con-
form to any strict plan ; the
Fig. 184.-A, Apical view ; B, front view of ripe initial cells are oblong, seeu in

sporangium of O. cinnamomea ; r, annulus, , , , « 1 /•

X45. • vertical section, and the first

divisions are longitudinal, so
as to meet the basal wall : both in the segment thus cut off and
in the central cell, periclinal or sometimes oblique divisions may
take place, so that a considerable bulk of tissue is formed, in
the projecting apex of which a single large cell occupies a
central position." Like Botrychium the archesporium is derived
from a single hypodermal cell, which approaches more or less

* Lachmann (7), p. 118. ^ Bower (11), p. 362 ; Goebel (17), p. 387,

THE HOMOSPOROUS LEPTOSPORANGIAT^

357

the tetrahedral form of the true Leptosporangiates, but shows a
good deal of variation. As in these the wall of the sporangium
is only one-layered, and the tapetum ordinarily two, but
occasionally three-layered. The fully-developed sporangium is
in shape much like that of Botrychium Virginianum, and has
a very short massive stalk. Like Helminthostachys and
Angiopteris, it opens by a vertical cleft, and like the latter
there is a rudimentary annulus consisting of a group of thick-
walled cells (Fig. 1 84, r).

The GleicheniacecB

These comprise about twenty-five species of tropical and

irhirVi mav hf» all nIarpH in two crpnpra ^

These comprise about twenty-five species of tropical i
sub-tropical Ferns, which may be all placed in two genera ^

Fig. 185.— a, Pinnule of Gleickenia dichotoma (Willd.). showing the position of the son (j), X4 ; B,
ventral ; C, dorsal view of the ripe sporangium, x 85 ; D, vascular bundles of the petiole and
stem of Gleichenia (sp.) (after PoiraultX The dark masses represent the xylem masses ; ph,
phlo€m ; r», endodermis.

Platyzoma^ with a single species P, microphyllum, and Gleichenia,
The best known is G. dichotoma^ an extremely common Fern of

* Hooker and Baker ( i ).

353 MOSSES AND FERNS chap.

the tropics of the whole world. It has very long leaves, which
fork repeatedly, and may be proliferous from the growth of buds
developed in the axils of the forked pinnae.

The development of the prothallium has been studied by
Rauwenhoff,^ and shows some interesting points in which it is
intermediate between the Osmundaceae and the other Leptospor-
angiatae. The spores of Gleiclienia are usually tetrahedral, and
contain no chlorophyll. When the ripe spores are sown, after a
few days the oil-drops become much smaller but more numerous,
and the first chloroplasts become evident. The latter increase in
number and size, and small starch grains are developed. The
exospore is ruptured in from two to three weeks from the time
the spore is sown, and the spore contents surrounded by the
intine project through the opening. The first wall usually
separates the first rhizoid, which, like that of Osfnunda^ often
contains a good deal of chlorophyll, from the larger prothallial
cell. As a rule the development of the prothallium corresponds
closely to that of tKe Polypodiaceae, but it may have a midrib
like that of Osmunda. The growth is normally from a two-
sided apical cell, which is replaced later by marginal initials.
A point of resemblance to Osmunda is the abundant production
of adventitious shoots, which are formed in numbers upon the
margin or from the ventral surface, and may develop into
perfectly normal prothallia.

RauwenhofFs account of the sexual organs is not as
complete as might be wished, but is sufficient to show some
interesting points of resemblance to the Osmundaceae. The
first wall in the antheridium cuts off a basal cell, and the next
wall is somewhat like the funnel-shaped wall in the Polypodi-
aceae. The dome-shaped wall next formed is here not so
marked, being nearly flat.^ No definite cover cell is cut off,
but the upper cell appears to divide by a single wall running
obliquely over the apex, somewhat as in Osmunda, The
divisions in the central cell offer no peculiarities, and the
spermatozoids resemble those of other Ferns. The archegonia
are formed on the forward part of the midrib, but are not
confined to the sides, as in Osmunda, Apparently a basal cell

^ Rauwenhoff (i).

' Rauwenhoff's statement that the central cell of the antheridium contains chloro-
phyll, to judge from his Fig. 58, which illustrates this, is based upon a pathological
case. The absence of chlorophyll from the central cells of the antheridium is a very
constant character ih all Archegoniates.

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 359

is not formed, but as to this and the much more important
point, the number and character of the canal cells, Rauwenhoflf
says nothing definite. The neck is long and straight, like that
of Osmunda and the Hymenophyllaceae.

The Embryo

To judge from the few rather vague statements made by
Rauwenhoff in regard to the embryo, this more nearly resembles
the typical leptosporangiate type than it does Osmunda. The
primary root has a large and definite three-sided apical cell,
and the divisions in the segments are very regular.

Poirault ^ has recently made a study of the stem of various
species of Gleicfteniay which differs a good deal from that of
Osmunda^ and approaches that of the Hymenophyllaceae and
Schizaeaceae. A single axial bundle traverses the stem, and is
separated from the sclerenchymatous cortex by a distinct
endodermis. Within the latter is a pericycle of several layers
of cells, within which is a continuous zone of phloem containing
large and small sieve-tubes, and phloem parenchyma. Within
the phloem are also secreting cells. The whole central part of
the stem is occupied by bundles of large scalariform tracheids
separated by parenchyma (Fig. 185, D). The single bundle
traversing the petiole is much like that of Osmunda^ and the
lamina of the leaf does not show any peculiarities.

The development of the sporangium is still unknown, but
it probably does not differ essentially from that of the
Hymenophyllaceae, with which it closely agrees in its mature
condition. In G, dichotoma (Fig. 185) the sporangia form
rounded naked sori above the terminal branch of a lateral vein.
They are pear-shaped, with a very short stalk, and upon
the outer surface is a nearly complete very distinct annulus
composed of a single row of large thick-walled cells. This is
interrupted at the top of the sporangium by three or four
narrow thin -walled cells, and starting from this point and
extending along the median line of the ventral surface are two
rows of narrow cells, between which the sporangium opens.

1 Poirault (l), p. 170.

36o MOSSES AND FERNS

The Hymenophyllacece

The Hymenophyllaceae have been the subject of much
discussion on account of the assumption made by all the
earlier writers that they were the most primitive of the
Pteridophytes. This was based very largely upon the apparent
resemblance between the delicate sporophyte of many of them
and the leafy gametophore of the Mosses. More recent study
of their development, especially the gametophyte, has led to a
modification of this view, although it is still held by many
botanists. It seems more probable that the peculiarities of
both gametophyte and sporophyte are due to the peculiar
environment of these plants, which grow only in very moist
places, indeed are almost aquatic at times. They are for the
most part extremely delicate Ferns, of small size, and with feu-
exceptions are exclusively tropical. Many are epiphytes, and
these have the roots very poorly developed or even entirely
wanting. The leaves are, with few exceptions, reduced to a
single layer of cells, except the veins, which gives them a
striking resemblance in texture to the leaves of some of the
larger Mosses, e,g. species of Mntum. Hooker ^ reduces them
all to three genera, which, however, are often further divided.
Of these Loxsoma is represented by but one species, L. Cun-
ninghamii^ a form which seems to be intermediate in general
characters between the Cyatheaceae and the other Hymeno-
phyllaceae, but its life history and anatomy are not known.
Of the other genera Hooker gives seventy-one species to
Hymenophyllutn and seventy-eight to Trichomanes?

The Gametophyte

The gametophyte is known more or less completely in
several species of both Tricliomanes and Hymenophyllum. The
large spores germinate promptly, but their subsequent develop-
ment is very slow. They contain chlorophyll, and often begin
to germinate within the sporangium, where they may often be
found divided into three equal cells by walls radiating from
the centre (Fig. i86). All of the cells begin to grow out

* Hooker and Baker (i).
' The number of species known now considerably exceeds this.

THE HOMOSPOROUS LEPTOSPORANGIATA:

361

into filaments, but usually only one of them develops into the
prothallium, the others dividing only once or twice, and forming

Fig. 186. — Trickonianti Draytonianum (Brack). Germination of the spores, X525; r, primarj'

rhizoid.

short brown rhizoids. In some species of Trichomanes^ e.g.
T. pyxidiferum} the prothallium remains filamentous, and
forms a densely branching structure very much like the

Fig. 187. — Hymenopkyllum (*». A, Large prothallium of the natural sire ; B, part of the margin of
one of the growing branches, showing two similar initial cells, X180; C, a filamentous male
prothallium derived from a bud, x6o.

protonema of some Mosses, but coarser in texture. Other
species, however, e.g, T. alatum^ produced flattened thalloid

» Bower (8).

362

MOSSES AND FERNS

prothallia from branches of the filamentous forms, and
Hymenophyllutn always has a flat hepatic-like prothallium, which
in its earlier stages, according to Sadebeck,^ always develops a
two-sided apical cell, and differs in no wise from that of other
Ferns. These prothallia, however, remain single - layered
throughout, although they reach an extraordinarily large size,
and branch much more freely than those of any other Ferns
(Fig. 187). The root-hairs are always very short and dark-

FiG. 188. — Hymenophyllum {sfy. Margin of a prothallium with numerous gemms k; X85 ;
B, a young gemma, x 260 ; f /, its stalk.

coloured, and generally occur in groups upon the margin only.
The branching of the prothallia is either monopodia! or
dichotomous, and the latter method may be repeated a number
of times. They may live for an indefinite time apparently.
The writer has kept prothallia of both Trichomams and
Hymenophyllum for nearly two years, at the end of which time
they showed no diminution of vigour.

They form ordinary adventitious shoots, but there are also

1 Sadebeck (6), p. 161.

XI THE HOMOSPOROUS LEPTOSPORANGIAT.£ 363

special gemmae developed in many of them, often in great
numbers. In an undetermined species of Hymenophyllum col-
lected in the Hawaiian Islands (Fig. 188) these gemmae
occurred very abundantly upon prothallia that had ceased to
form sexual organs. Here a marginal cell grew out and curved
upward, and the tip was cut off by a transverse wall from the
basal cell. In the terminal cell are next formed a series of
vertical walls, which transforms it into a row of cells extended
at right angles to the axis of the pedicel. One of the central
cells now bulges out laterally, and this papilla is cut off by
an oblique wall and forms the beginning of a short lateral
branch, so that the fully- developed bud has somewhat the
form of a three-rayed star, and in this condition becomes
detached and grows into a new prothallium. The prothallia
formed in this way often do not develop a flat thallus, but may
remain filamentous, and each ray may produce antheridia either
terminally or laterally (Fig. 187, C). In case a flat thallys is
formed, only one or sometimes two of the rays grow out in this
form, the other having only a limited growth, and terminating
in a short rhizoid. In short, the process is very similar to
that in the germinating spores.

TJie Sexual Organs.

Bower ^ has investigated the structure of the antheridium
in Trtc/tomaneSy and Goebel ^ both Tricltomanes and Hymeno-
phyllum. My own study of their development has been
confined to an undetermined species of Hymenophyllum from
the Hawaiian Islands, but the results of my observations agree
entirely with those of other observers. The antheridia arise
mainly upon the margin of the prothallium, or upon the ends
of the filamentous ones. After the mother cell is cut off, there
is usually formed another transverse wall, by which a short
pedicel is produced. A funnel-shaped wall does not ever seem
to be formed, but the next division walls are more like those
in Osmunda^ and extend only part way round the circumference
of the mother cell. After a varying number of basal cells aire
thus formed, a dome-shaped wall arises, separating the central

» Bower (8).

* Goebel, Ueber epiphytische Fame und Muscineen. Ann. dujardin botanique
de BuiUnzorg, vol. vii.

3^4

MOSSES AND FERNS

CHAP.

cell. This wall is not so convex, as is usually the case in the
Polypodiaceae, and in this respect, as well as the form of the
wall cells, the antheridium resembles that of Gleichenia. In
the Hymenophyllaceae no cap cell is formed, but as in Osmunda
and Gleichenia, the upper cell is divided by walls running over
the apex. The divisions in the central cell and the structure
of the spermatozoids, so far as these have been studied,
correspond with those of the other Leptosporangiatae.

A single archegonial cushion is not formed, but the
archegonia occur in small groups at different points upon the

Fig. iix),—HymenophyUum (sfi). Development of the antheridium, xa6o. A, D, From living
specimens; E, microtome section ; B i, C 2, D i, optical sections; B 2, C i, D 2, surface view
of the same.

margin. Goebel ^ has shown, however, that these archegonial
groups arise first near the growing point of the prothallial branch,
and that they are simply separated by the intervention of zones
of sterile tissue. At the point where they arise the prothallium
becomes more than one cell thick, and in all cases where the
development could be certainly followed, the archegonium
arose from one of the ventral cells, and never directly from a
marginal cell. The details of the development have not been

* Goebel, Ueber epiphytische Fame und Muscineen. Amt. du Jardin boianiqut
de Buitenzorg^ vol. vii. p. 105.

THE HOMOSPOROUS LEPTOSPORANGIAT^

365

followed, and whether there is any division of the neck canal
cell is not known. The neck is straight, as in Osmunda and
Gleichenia,

In Tridiomanes the archegonial meristem (archegoniophore)
may be formed as a short branch, directly upon the filamentous
prothallium.

The lateral walls of the prothalHal cells are in all the forms
thicker than is the case in most Ferns, and there are distinct pits
in them. In the root-hairs a parasitic fungus is frequently found.

Fig. 190.— Pinna of ihc leaf of HymenophyUnm recunmm (Gaud.), x 3 ; B, part of rhixonie (r) and
leaf of Trichomanes parxmlum (Poir.), X 3 ; C, pinna of the leaf of Trichontanes cyrtothcca
(Hilleb.X X3; D i, trumpet-shaped indusiuni of the same, X4; 2, section of the indusium {id)
with the central sorus, x 5 ; j, the sorus.

The embryogeny is almost unknown,^ but the first divisions
and the very young sporophyte correspond closely with those of
the other Leptosporangiatai. The cotyledon is simple with a
single median vein, and a root is present in all forms yet
examined.

TIte Mature Sporophyte

Prantl ^ has given a very complete account of the structure
of the mature sporophyte, and Bower ^ has added to this by a
careful study of the meristems of the different organs. From

Janczewski (2).

Pranll (i).

=* Bower (11).

366 MOSSES AND FEKNS chap.

the investigations of the latter it seems that here, as in nearly
all other Ferns, the .stem apex has the usual three-sided initial
cell, but only a small part of the segments give rise to leaves,
which are arranged in two ranks. As in Gleichenia, there is a
single vascular bundle in the stem, and this, according to Prantl,^
is collateral in HemipJdebium as in Osmunda, The tracheary
tissue lies upon the ventral side of the stem, the phloem on
the dorsal side. The pericycle,^ which at points shpws clearly
its common origin with the endodermis, surrounds the whole
bundle. The cortex is composed in part of parenchyma, and
partly of sclerenchyma. In the sub-genus Hentiphlebiutn the
latter occupies the periphery of the stem, in the others the
position is reversed, and it lies next the vascular bundle. In
the other forms also the stem bundle is concentric, and cor-
responds closely with that of Gleic/tenia.

Tlie Leaf

The observations on the earliest stages of the leaf are very
incomplete, but in some cases at least a two-sided apical cell \s
present. In those with palmately lobed or entire kidney-shaped
leaves, the later growth is marginal, and of the same type found
in similar leaves among the Polypodiaceae. The venation in
these forms is exclusively dichotomous, in those with pinnate
leaves, e,g, Trichomanes radicans^ this is only true of the last
formed veins.

With the exception of a very few species, ^.g, T, reniforme,
H. dilatatum, where the mesophyll of the leaves is three to four
cells thick, the whole lamina, with the exception of the veins, is
single-layered, and of course stomata are completely absent.
The form of that leaf is either pinnate, as in the larger species
of Trichomanes and Hymenophyllum (Fig. 190), reniform {T,
reniforme\ or palmately divided {T, parvulum^ Fig. 190, B).
The smaller veins, as in other Ferns, have collateral vascular
bundles, and in the smallest ones the xylem may be reduced to
a single row of tracheids. The latter may be spiral, reticulated,
or scalariform. In the phloem Prantl could not distinguish any
well-marked sieve-tubes, but it was mainly composed of bast

* Prantl (i), p. 26.

* Van Tieghem (3) considers the endodermis to be double, and thai no true
pericycle is present.

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 367

fibres and cambiform cells, and in Hefniplilebiuni {Trichomanes)
Hookeri the phloem is absent from the very much reduced
smaller veins. This is possibly an intermediate condition
between the normally developed bundles of the veins of most
species and the so-called pseudo-veins, in which there is no
tracheary tissue developed, but which in their origin correspond
to the ordinary veins. The petiole always has a single vascular
bundle, usually of typical concentric structure, but in the section
Hemiphlebium Prantl ^ states that it is collateral. The ground
tissue of the petiole is largely composed of sclerenchyma like
that of the stem.

The Roots

The development of the roots has been studied only in a
very few forms. Bovver^ states that in 71 radicans and H.
demissum it "conforms to the normal type for the root of
leptosporangiate Ferns, as described by Nageli and Leitgeb ,"
but does not go into details, and Prantl^ makes an equally
brief statement. While lateral roots are completely wanting in
the section HemipUebium, where their place is taken by leafless
branches, in most of the other forms they are developed in
considerable numbers. There is, according to Prantl,* great
variation in the arrangement of the parts iif the vascular
cylinder. Thus while all the species of Hymenophyllum have
diarch bundles, that of Trichomanes pyxidiferum is monarch,
while in one species, T, brachypuSy as many as nine primary
xylem masses were found. The Marattiaceae alone, among the
other Ferns, show this great variability.

Trichomes occur, but not so abundantly as in most of the
Leptosporangiatae. They have mostly the form of hairs, which
are either temporary (those formed on the margins of the young
leaves) or persistent for a longer time, like those that cover the
end of the stem apex and bases of the petioles in many
species.

Tlie Sporangium

All of the Hymenophyllaceae agree closely in the position of
the sporangia, whose development has, however, been studied
only in Trichomanes ; but from the close correspondence in

> Prantl (i), p. 26. ^ Bower (11), p. 30S.

» Prantl (i). ■* Prantl, Lc.

368

MOSSES AND FERNS

CHAP.

other respects it is not likely that Hynienophyllutn differs essen-
tially from the latter. The sorus occupies the free end of a vein,
which often continues to grow for a long time in Tricliomams^
and forms a long slender placenta or columella, upon which the
sporangia arise basipetally. While the receptacle is still very

P'iG. 191. — Tricttomants cyrtotheca (Htlleb.)> Development of the sporangium, X235. A, Longi-
tudinal section of very young receptacle with the first sporangia (4/) ; B-D, successive stages of
development seen in longitudinal section ; F, horizontal section of nearly ripe sporangium ; r.
the annulus.

young the tissue of the leaf immediately about it forms a ring-
shaped ridge, which grows up in the form of a cup-shaped
indusium, which either remains as a tube {Trichmnanes) or is
divided into two valves {^Hymenophyllum\ Many species of the

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 369

former genus, however, show an intermediate condition, with the
margin of the indusium deeply two-lipped.

The first sporangia arise at the top of the placenta (Fig. 191),
but the apex itself does not usually develop into a sporangium.
Afterthe first sporangia have formed, new ones continue to develop.
Near the base of the placenta a zone of meristem is formed, which
constantly contributes to its growth, and the young sporangia arise
from the surface cells formed from this meristem. The mother cell
is very easily distinguished by its larger size and denser contents.
About every third cell seems to develop a sporangium, but this
probably is not absolutely uniform. The first wall is usually
nearly vertical, and cuts off a narrow segment from one side of the
mother cell (Fig. 191, A). This in most cases examined was
next followed by a wall almost at right angles, forming a small
basal cell. After these preliminary divisions, which form the
very short stalk, the next divisions are exactly as in the Poly-
podiaceae, and give rise to the central tetrahedral cell with the
four peripheral ones. Prantl ^ states that the first divisions of the
cap cell are also spirally arranged. In T.cyrtotluca (Fig. 191)
the tapetum is massive, and composed throughout of two layers.
The archesporium divides into eight cells, whose further history
is the same as in other Ferns. The annulus in the Hymeno-
phyllaceae is large, and situated much as in Gleichenia,
According to Prantl^ it arises in part from the cap cell and
partly from numbers one and three of the primary peripheral
cells. Where the young sporangium is cut longitudinally
(Fig. 191), the annulus cells are at once recognised by their
larger size, especially upon the dorsal side. Their radial and
inner walls become very thick, and a horizontal section (Fig. 191)
shows that the annulus is not complete, but is interrupted on the
inner side where the stomium is formed.

Apogamy and Apospory

Both of these phenomena have been discovered by Bower ^
to occur not infrequently in Tricliontanes, and probably further
investigations will reveal other instances. Apogamy was com-
mon in 71 alatum, in which species archegonia were not seen at
all, and the origin of the young sporophyte was unmistakably
non-sexual. Prothallia, arising directly from the leaf, or from

1 Prantl (1), p. 39. * Prantl, I.e. p. 40. » Bower (8).

2 B

370

A/OSSES AND FERNS

the sporangial receptacle, were found to be a common pheno-
menon in the same species.

The Schizcsacece^

The Schizaeaceas include about sixty species belonging to
five genera. The very characteristic sporangia have a terminal
annulus, which forms a sort of crown at the apex. Some of
them, like Schizcea pusilla and Trochopteris eleganSy are very small

Fig. 192. —Lygodiuin Japonicnm (Sw.). A, Pinnule, X3 ; j, the sporangial segments ; B, horizon-
tal section of one of the latter showing the sporangia, */, x 14 ; C, a single sporangium, sbofwing
the terminal annulus (r), x 65 ; D, cross*section of the petiole, x 65.

and delicate species ; the largest species of Lygodium have
fronds 2 or 3 metres in length, but always slender and delicate
in texture.

The development of the prothallium corresponds closely to
that of the Polypodiaceae,^ but there are one or two peculiarities.
The spores are always of the tetrahedral form, and without
chlorophyll. The germination follows as in the Polypodiaceae,

Praml (5).

Bauke, Pringsheims Jahrb. f. wiss. Botanik, vol. xi.

XI THE HOMOSPOROUS LEPTOSPORANGIAT^ 371

and a filament is first formed, after which the flat prothallium
grows for a time by a single apical cell, which is finally replaced
by a group of marginal cells. In Aneimia and Mohria the
growing point lies on one side, so that the prothallium is not
heart-shaped. In Lygodium} however, the prothallium has the
ordinary form.

The development of the antheridia has been studied by
Kny^ in Aneimia hirta. The only difference between this and
the normal antheridium of the Polyppdiaceae is that in Aneimia
the first wall is always flat instead of funnel-shaped, and the
basal cell of the antheridium is therefore disc-shaped. The
archegonia appear to correspond exactly with those of the
Polypodiaceae.

The tissues of the sporophyte in Lygodium and Schizcea are
much like those of Gleichenia and the Hymenophyllaceae. As
in these the stem is traversed by a single concentric vascular
bundle, as well as the petioles. In Aneimia and Mohria the
bundles of the stem form a cylindrical network like that of the
Polypodiaceae. The stem bundles are concentric, as are those
of the petiole and larger veins in all but Schizcea^ which Prantl ^
states has collateral bundles throughout, except in the stem.
The small veins have collateral bundles as in other Ferns.
Sclerenchyma is largely developed, especially in the petioles,
where the whole mass of ground tissue in Lygodium (Fig. 192)
is composed of this tissue.

The leaves are pinnate in all the forms except a few species
of Schizcea, Lygodium^ as is well known, shows a continuous
growth at the apex of the leaf, something like Gleiclunia,
but here the primary apex retains its meristematic condition, and
the extremely long and slender axis of the leaf twines about its
support like the stem of many climbing plants. The sporo-
phylls are usually smaller than the sterile leaves, or where only
portions of the leaf are sporiferous these are much contracted.
The anatomy of the leaf corresponds closely with that of the
other Ferns. The stomata, which are for the most part con-
fined to the lower side of the leaf, are always arranged in two
parallel rows in Schizcea^ and the peculiar stomata of Aneimia
have already been mentioned. The trichomes are for the most
part hairs. Only in Mohria do scales occur.

The leaves arise from the upper side of the creeping stem,

» Bauke, Bot. Zeil. 1878. .« Kny (4). ' Prantl (5), p. 23.

372 MOSSES AND FERNS chap.

and in Lygodium^ Prantl ^ states that they form but a single
row. He also says that the roots are always diarch, like the
Polypodiaceae, but gives no further details of their growth or
structure.

TJie Sporangia

The development of the sporangia has been carefully in-
vestigated by Prantl,^ and in origin and arrangement they
differ decidedly from the other Leptosporangiates, but approach
most nearly Osmunda^ and among the eusporangiate Ferns
show a certain likeness to Botrychiunt, The sporangia arise
always in acropetal order from the apex of the terminal seg-
ments (sorophore) of the sporophyll, and are strictly lateral in
origin, not originating from epidermal cells, but from marginal
ones. The young sporangium appears as a lateral outgrowth
of the margin, exactly like a young pinna upon the main axis,
and the young sorophore has the appearance of a young
pinnate leaf, and at this stage recalls strongly the similar one
in Botrychium, This is especially marked in Aneimia and
LygodiufHy less so in Schizcea, where the sporangia are smaller,
and the mother cells project much more strongly. The early
divisions correspond closely with those of the Hymenophyllaceae,
and as there the tapetum is massive and two-layered, and the
stalk of the sporangium very short. The wall is derived in
major part from the cap cell, which in all the forms becomes
much more developed than in any other Ferns, and from it
alone the apical annulus is derived.' In Aneimia and Mohria
the tissue of the tip of the leaf adjacent to the sporangia grows
into a continuous indusium, which pushes them under to the
lower side. In Lygodium (Fig. 192) each sporangium very
evidently corresponds to a single lobe of the leaf segment, and
has a vein corresponding to this. The pocket-like indusium
surrounding each sporangium grows up about it much as the
indusium of Trichomanes grows up about the whole sorus.

The Cyatlieacece

These are all Ferns of large size, some of them tree-Fems,
10 metres or more in height. They occur in the tropics of

1 Prantl (5). » Prantl, Lc.

• The divisions in the wall are too complicated to be explained without numerous
figures. See Prantl's figures, Plates V.-VIII.

xr THE HOMOSPOROUS LEPTOSPORANGIATyE 373

both hemispheres, and some of them, e,g. Dicksonia antarctica^
are also found in the extra -tropical regions of the southern
hemisphere. They correspond so closely in all respects with
the typical Polypodiaceae that, except for the slightly different
annulus, they might be placed in that family. In some forms,
e,g, Alsophila contaminanSy the trunk is quite free from roots,
and the leaves fall away, leaving very characteristic scars marked
by the vascular bundles. In others, like Dicksonia antarctica,
the whole trunk is covered with a thick mat of roots, thicker
than the trunk itself.

The prothallium is exactly like that of the Polypodiaceae,
so far as it has been studied,^ except that in some species of
Alsophila there are curious bristle-like hairs upon the upper
surface. In the structure of the antheridia the Cyatheaceae are
intermediate in character between the Polypodiaceae and the
Hymenophyllaceae. The characteristic funnel-formed primary
wall of the former occurs here, but not until one and sometimes
two preliminary basal cells are cut off, as in Osmunda or
Hyntenophyllum, The following divisions correspond exactly
with those of the antheridium of the Polypodiaceae, except that
Bauke states that the cap cell, as well as the upper ring cell, may
divide again. The dehiscence is effected either by the separa-
tion of an opercular cell or by the rupture of the cap cell. The
archegonia are like those of the Polypodiaceae. In Cyathea
medullaris Bauke figures a specimen, however, where the neck
canal cell is divided by a membrane.^

The first divisions in the embryo correspond with those of
the Polypodiaceae, but the further development of the young
sporophyte is not known.

The position of the sori is that of the typical Polypodi-
aceae, and sometimes a decidedly elevated placenta is present.
The indusium is either cup -shaped {CyatJieay Alsophila) or
bivalve, e,g, Cibotiutn (Fig. 193). In the latter the outer valve
fits closely over the other like the cover of a box. The
sporangia, which are either long or short-stalked, although their
development has not been followed, correspond so closely in the
mature state to those of the Polypodiaceae that there is little
doubt that their development is much the same. The annulus
is nearly or quite complete, but above the stomium in Cibotium
Menziesii the cells of the annulus are broader but thinner-walled
i Bauke (I). '^ Bauke, I.e. PI. IX. Fig. 8.

374

MOSSES AND FERNS

(Fig. 193, C), and Atkinson shows much the same appearance
in C Cliamissoi, In the former species the stalk is long and
composed of three rows of cells, as in typical Polypodiaceae.
With the sporangia in this species are also numerous long
paraphyses (Fig. 193, D).

The very interesting genus Matonia is represented by the
two species M, pectinata and M, sarmentosay the latter but
recently discovered. Both belong to the Malayan Archipelago,

Fig. igi.—CibotiutM Memiesii (KaulO* A, Pinnule with the sori (x), X3; B, a single !>oni>
showing the two-valvcd indusium, x 9 ; C, a single sporangium, x 80 ; r, the annulus ; D. a
paraphysis, x8o.

and are very restricted in their range. From a study of the
latter species Baker ^ concludes that the genus is the type of
a special family intermediate between the Gleicheniaceae and
Cyatheaceae. The indusium is umbrella-shaped, and firm in
texture, and the sporangia are arranged in a circle about its
base.

Zeiller,^ from a comparison of Matonia with the fossil genus

1 Baker (3). « Zeiller(i).

XI THE HOMOSPOROUS LEPTOSPORANGIATAl 375

Laccopteris, which occurs in early Jurassic beds, concludes that
the two genera are very near each other if not identical, and
represent the earliest forms of the Cyatheaceae, and that Matonia
is the last remnant of a group which is now in process of
extinction.

The Polypodiacece

The Polypodiacese may very aptly be compared to the
stegocarpous Bryincae among the Mosses, inasmuch as like that
group they give evidence of being the most specialised members
of the order to which they belong, and compose a very large
majority of the species. Most of them agree closely in their
structure, which has been given in detail, and will not be
repeated here. With very few exceptions the structure of the
prothallium and sexual organs is like that of OnocleUy but one
or two variations may be mentioned. In Vittaria^ Goebel ^
has found a type of prothallium recalling that of Hymenophylluvi,
both in its large size and extensive branching. Its earlier
stages show the ordinary development, but it later branches
extensively, and, like Hymenophyllum^ numerous groups of
archegonia are formed upon one prothallium. Bodies resem-
bling the oil bodies of Liverworts are also met with in this
genus. The sexual organs closely resemble those of the
Polypodiaceac, but the antheridia have a well-marked stalk,
something like that found often in the Hymenophyllaceae.
Another aberrant genus is Ceratopteris, which differs so much in
several respects that it has sometimes been regarded as the
type of a separate family.^ It is, unlike all other homosporous
Ferns, a genuine aquatic, and no doubt this anomalous habit
has something to do with its peculiarities, especially the im-
perfect development of the ring of the sporangium, which,
according to Hooker,' is often met with.

The prothallia show some peculiarities as well. Thus, while
the early stages are like those of other Polypodiacese, the arche-
gonial meristem is developed, not from the apex of the
prothallium, but laterally, and quite independent of the original
growing point, which is pushed to one side. The antheridia
are of the polypodiaceous* type, but project less than in the
other forms. The sporangia are very large, but correspond in
their development with that of the other Polypodiaceae.

» Goebel (9). 2 Kny (6). » Hooker (i), p. 174.

376

MOSSES AND FERNS

Among the many genera and species aside from these, while
there is extraordinary variety, the differences are all of
secondary importance, and consist mainly in the form and

Fig. 194.— a, Pinnule of Aspidium spinulosum (Schw.X showing the son (j) with kidney-fhapcd
indusium, X4; B, cross-section of a pinna from a young sporophyll of OnocUa strutkiopUris ;
s, sorus, X40.

venation of the leaves and the position of the sporangia. The
leaves range from the undivided ones of Vittaria or Scolopen-
drium to the repeatedly divided leaves, usually pinnate, of such
forms as Pteris Aquilina, In some tropical epiphytic species,

such as Asplenium nidus^ Platy-
ceriufHy species of Polypodium, the
leaves are arranged so that they
form receptacles for collecting
humus. In the two latter genera
these leaves are very much modi-
fied, the two forms of leaves being
familiar to all botanists in the
common Platycerium alcicome^
where the closely overlapping
round basal ones are very highly
developed.^

The sporangia may almost
completely cover the backs of
the sporophylls, as in Platy-
cerium^ or more commonly form
definite sori, which may or may not have an indusium. Where

1 Goebel, Ueber epiphytische Fame und Muscineen. Antu dtijardin botanique <U
BuUtnzorg^ vol. vii.

Fig. 195.

Pinna from the leaf of Cystopteris
bulbi/era (Bemh.), with a bud (*) at the
base, X a ; #, the sori (after Atkinson).

XI THE HOMOSPOROUS LEPTOSPORANGIATAl 377

the latter is present, it is either formed by the margin of the
leaf, as in Adiantum or Pteris, or it may be a special scale-
like outgrowth of the lower side of the leaf. In such cases it
forms a membraneous covering of characteristic form. Thus
in Aspidium (Fig. 194, A) it is kidney -shaped, in Asplenium
elongated, and free only along one side. Where, as in Onoclea
(Fig. 194, B), the margins of the sporophyll are involute, so as
to completely enclose the sori, the indusium is wanting or very
rudimentary.

CHAPTER XII

LEPTOSPORANGIATiE HETEROSPOREif- (HYDROPTERIDES)^

The two very distinct families of heterosporous Leptospor-
angiatae have obviously but little to do with each other, but,
both of them being evidently related to the homosporous forms,
they may be placed together for convenience. Each of the t\vo
families contains two genera, which in the Marsiliacese are
closely allied, but in the Salviniaceae not so evidently so,
although possessing many points in common. They are all
aquatic or amphibious plants, and the gametophyte, especially
in the Marsiliaceae, is extremely reduced.

Salviniacece

The two genera, Salvinia and Azolla, contain a number of
small floating aquatics which differ very much in the habit of
the sporophyte from any of the other Filicineae, but in the
development of the sporangia and the early growth and form
of the leaves show affinities with the lower homosporous
Leptosporangiatae, from some of which they are probably
derived.

The fully -developed sporophyte is dorsiventral, and the
leaves are arranged in two dorsal rows in AzoUa, four dorsal
and two ventral in Salvinia, The dorsal leaves are broad and
overlap, so that they quite conceal the stems. Roots are
developed in Azolla, but are quite wanting in Salvinia, where
they are replaced physiologically by the dissected ventral
leaves (Fig. 196). The sporophyte branches extensively, and
these lateral shoots readily separate, and in this way the plants

* Also known as Rhizocarpeje.

CHAP. XII LEPTOSPORANGIA_TA£ HETEROSPOREAi

379

multiply with extraordinary rapidity. The sporangia are
enclosed in a globular or oval " sporocarp," which is really an

Fig. \^.—Salvinia natatu (L.). A, Small plant, Xa, seen from above; B, a similar one from
below; w., root-like submerged leaf; C, fragment of a fruiting plant, Xa; x/, sporocarps;
D, a macrosporangial (ma) and microsporangtal {mi) sporocarp in longitudinal section (slightly
magnified) ; £, male prothallium with the single antheridium (an) from the side, x looo ; F, a
similar one seen from above : G, spermatozoid (Figs. C, D after Luerssen).

indusium, much like that of some of the Hymenophyllaceae ancl
Cyatheaceae.

38o MOSSES AND FERNS chap.

T/te Ganietophyte

The first account of the development of the sexual stage
of the Salviniaceae that is in the least degree accurate is
Hofmeister's,^ who made out some of the most important points
in the development of the female prothallium. Pringsheim's* 1
classic memoir on Salvinia added still more, as well as Prantl *
and Arcangeli/ but none of these observers were able to follow
accurately the earliest divisions in the germinating macrospores.
Berggren's ^ account is the only one on the female prothallium
of Azolla, except a paper by the writer, but Belajeflf * has given
an excellent account of the germination of the microspores.

Tlu Male Protliallium

The microspores at maturity are embedded firmly in a mass
of hardened protoplasm, which in Salvinia fills the whole
sporangium, in Azolla is divided into separate masses, " mas-
sulae." The wall of the sporangium in Azolla decays and sets
these free in the water, but in Salvinia the wall of the
sporangium is still evident when the germination takes place. In
the latter the young prothallium grows into a short tube, whose
basal part is separated as a large vegetative cell, from whose
base later, Belajeff ^ states, a small cell is cut off. The upper
cell becomes the antheridium. In it is first formed in most
cases an oblique wall, which Belajeff states is always followed
by another similar one, which forms a central sterile cell
separating the two groups of sperm cells. This cell, however,
did not occur in the specimens studied by me, when the two
groups of sperm cells were usually in immediate contact (Fig.
1 96, E). From each of the upper cells peripheral cells are cut
ofT, but they do not completely enclose the sperm cells, which
are in contact with the outer wall of the antheridium. A cover
cell corresponding to that in the ordinary Fern antheridium is
more or less conspicuous. Each of the central cells divides
by cross-walls into four, and there are thus eight sperm cells in
the ripe antheridium. The spermatozoids of Salvinia have
about two complete coils, and a smaller number of cilia than is
usually the case in the Filicineai (Fig. 196, G).

* Hofmeister (i), p. 328. ^ Pringsheim (i). * Prantl (4). ■• Arcangeli KW
* Berggren (2). « Belajeff (3). ^ Belajeff (3) in Bot. CentralblaU, 1892, p. 328.

LEPTOSPORANGIAT^ HETEROSPOREjE

381

In Azolla the contents of the ungerminated microspore,
whose wall is thin and smooth, contain but little granular
matter. The first indication of germination is the rupturing of
the exospore along the three radiating ventral ridges, and the
protrusion of a small papilla. This is cut off by a transverse
wall near the top of the spore cavity, and forms at once the
mother cell of the single antheridium (Fig. 197, C). Belajeff^
says the next divisions are nearly parallel and divide the
antheridium into three cells, one above the other, and of these

Fig. 197' — Azolla filiculoidcs (Lam.). A, Massula with enclosed microspores (j/), x 250 ; gl,
glochidia: B-D, development of male prothallium and antheridium, X560 ; ^, opercular cell ; £,
two cross-sections of a ripe antheridium, x 750 ; i, the top ; 2, nearly median section.

only the middle ones divide further. For some reason, which
is not quite clear from his account, Belajeflf does not regard the
whole upper cell as an antheridium, but says that the latter is
only formed after five vegetative cells have been cut off". It
seems much more in accordance with the structure found in the
related homosporous Ferns to regard the whole upper part of
the prothallium as the antheridium. In spite of his statement
that the development of the male prothallium has little in

1 Belajeflf (3), p. 329.

382 MOSSES AND FERNS chap.

common with the true Filices, his figure of Asolla is extra-
ordinarily like the simple male prothallia that sometimes occur
among the Polypodiaceae. The small cell, cut off subsequently
from the basal cell, which he describes, I failed to find in any
of my sections, and the conclusion reached after careful study
was that but one vegetative cell (the large basal one) is formed,
and that the rest of the prothallium is to be regarded as a
single terminal antheridium.

The subsequent divisions correspond to BelajefFs account
In the middle cell of the antheridium two nearly vertical walls
are formed, which with the top cell (cover cell) completely
enclose the central one. The cover cell recalls in form and
position the same cell in the antheridium of the Polypodiaceae,
but is formed here previous to the separation of the central cell.
In one of the lateral cells a horizontal wall is formed, so that
the sperm cells are surrounded by five parietal ones. The
central cell now divides by a median vertical wall, and each of
the daughter cells twice more, so that eight sperm cells are
formed, as in Salvinia, The prothallium remains embedded in
the substance of the massula, and the spermatozoids probably
escape by the softening of the outer part of the latter. In
Salvinia the prothallia project beyond the sporangium wall, and
are easily separated.

The antheridium of the Salviniaceae does not closely
resemble that of any other group. Azolla differs less from the
homosporous Ferns in this particular, and shows some resem-
blance to the Hymenophyllaceae in the arrangement of the
parietal cells. Occasionally a triangular opercular cell occurs
in Azolla^ which recalls that in Osmunda.

TJie Female Prothallium

The macrospores of Azolla filiculoides are borne singly in
the sporangia. The spores only germinate after they have
been set free by the decay of the indusium, the upper part of
which, however, persists as a sort of cap. The decay of the
sporangium wall and indusium exposes the curious tuberculatc
epispore, with its filamentous appendJg^s, which serve to hold the
massulae, which are firmly anchored to them by their peculiar
hairs (glochidia) with their hooked tips* This is evidently of
advantage by bringing the male and female plants together.

XII LEPTOSPORANGIAT^ HETEROSPOREAi 383

The macrospores germinate most promptly in the early
autumn, and in California, where this species is abundant, this is
probably the natural time for germination. As the first stages
of germination take place within the completely closed spore,
it is difficult to tell precisely just when it begins. So nearly as
could be determined, the first division may take place within
two or three days, and the whole development be completed
within a week.

A section of the ripe spore, still within the sporangium,
shows its contents to be nearly uniform, and much like that of
Isoetes, The nucleus is here at the apex of the spore cavity
and not conspicuous. It is somewhat elongated and stains but
little. No nucleolus can be seen.

The first sign of germination is an increase in the size
of the nucleus, which becomes nearly globular, and a small
nucleolus becomes evident. At the same time the cytoplasm
about it becomes free from large granules and indicates the
position of the mother cell of the prothallium. This upper part
of the spore cavity is now cut off" by a nearly straight transverse
wall, and this small lenticular cell becomes the prothallium.
The granules in its cytoplasm are finer than those in the large
basal cell, and the nucleus stains strongly and shows a large
nucleolus. The nucleus of the lower cell remains in the upper
part, and is much like that of the prothallial cell.

The first division wall in the upper cell is vertical and
divides it into two cells of unequal size. In a prothallium
having but three cells, the second was also vertical, but in
others it looked as if it were horizontal, which Prantl ^ states is
the case in Salvinia. From the upper of the cells formed by
the first horizontal wall the first archegonium arises. If the
horizontal wall forms early, the primary archegonium is nearly
central, but if two vertical walls precede it, its position is
nearer the side opposite the first cell cut off. In the few cases
where successful cross-sections of the very young prothallium
were made, the archegonium mother cell was decidedly triangu-
lar, showing that it was formed by three intersecting walls, as
in Isoetes. It divides into an outer and inner cell, the latter,
as in IsoeteSy giving rise at once to egg and canal cells, without
the formation of a basal cell.

Up to this point the exospore remains intact ; the central

1 Prantl (4), p. 427.

384

MOSSES AND FERNS

CHAP.

cell of the archegonium is only separated from the spore
cavity by a single layer of cells, and the young prothallium
agrees closely with Prantl's account of the similar stage of
Salvinia (Fig. 198, A, B). Berggren's^ figures of A. Caro-
liniana, at a stage presumably the same, are too diagrammatic
to allow of a satisfactory comparison.

Shortly after the first division in the archegonium a rapid
increase takes place in the size of all the cells of the prothallium,
by which it expands and ruptures the exospore, which breaks
open by three lobes at the top.

Fig. ig&.—Azo/Za /ilicHloides (Lam.)> A, Longitudinal section through the upper pan of the
germinating macrospore, x 320 ; b^ 6, the basal wall of the proth.alliuin ; ar^ >^>ung arcbegoniam ;
n, free nuclei ; B, similar section of a nearly developed female prothallium, x 270 ; C, D.
archegonia, X375; k, neck canal cell ; v, ventral canal cell; o, egg; £, two transverse sectioos
of a prothallium with the three first archegonia, x 160 ; F, median section of a macrospore with
large prothallium (/^), X 65 ; t'n, indusium ; s/, remains of sporangium wall ; //, perinium.

The most remarkable difference between Azolla and the
other Hydroptcrides is the further development of the lower
of the two primary nuclei. In Azolla it undergoes repeated
divisions, and the resulting nuclei remain embedded in the
protoplasm in close proximity to the lower cells of the pro-
thallium (Fig. 198, A). This nucleated protoplasm is free
from the large albuminous granules in the lower part of the
spore cavity, and in stained sections presents a finely granular
1 Berggren (2), Figs. 7, 9.

XII LEPTOSPORANGIAT^ HETEROSPORE^ 385

appearance, and is evidently concerned with the elaboration of
the reserved food materials in the large spore cavity. In
exceptional cases indications of the formation of cell walls
between these nuclei were seen, but usually they remained
quite free. Whether a similar state of. affairs exists in Salvinia
remains to be seen.

When the first archegonium is ripe, the prothallium is
nearly hemispherical, with the originally convex base strongly
concave. The central cell of the archegonium is separated by
one, sometimes two, layers of cells from the spore cavity, and
the neck projects considerably above the surface of the pro-
thallium. The latter now pushes up between the softened
episporic mass at the top of the spore, and the archegonium
is exposed. In cross-section the prothallium is more or less
triangular (Fig. 198, E), with one angle longer than the others.
This longer arm corresponds to the " sterile third " of the
prothallium of Salvinia, and represents the first cell cut off
from* the prothallium mother cell.

If the first archegonium is fertilised, no others are formed ;
but usually several secondary ones are present. The second
archegonium arises close to the primary one ; indeed its
central cell is generally separated from it only by a single
layer of cells. The third forms near the base of the larger
lobe (Fig. 198, E). In case all of these prove abortive, others
develop between them apparently in no definite order, and to
the number of ten or occasionally more. In the older prothallia
these later archegonia are sometimes borne in small groups
upon elevations between the older ones.

The neck canal cell of the archegonium is formed much
earlier than Pringsheim describes in Salvinia, and is cut off
from the central cell about the time the first divisions take
place in the cover cell. Each row of the neck has four cells,
as in Salvinia, and the neck canal cell may have its nucleus
divide, as in Isoetes and the homosporous Filicineae. This has
not yet been observed in Salvinia.

In Salvinia ^ the prothallium is large and develops a good
deal of chlorophyll. It has a very characteristic appearance, and
shows the same triangular form that Azolla does, but from two
of the corners long wing-like appendages hang down, and the
whole prothallium is saddle-shaped. The side joining the two

* Pringsheim (i) ; Pranti (4).
2 C

386 MOSSES AND FERNS chap.

wings is the front, and the primary archegonium occupies the
highest point, as in Azolla, and the two secondary ones form a
line with it parallel to the forward edge, which develops a
meristem and other archegonia in rows parallel to the first
ones, in case these fail to be fertilised.

In Azolla the prothallium has but little power of independ-
ent existence, and even when unfertilised develops but little
chlorophyll. No root-hairs occur (this seems to be true of
Salvinia also), and the growth only proceeds until the materials
in the spore are exhausted. To judge from Berggren's figures ^
A. Caroliniana has a larger prothallium but fewer archegonia
than A, filiculoides,

T/te Embryo

The fertilised ovum, previous to its first division, elongates
vertically. The basal wall is usually transverse instead of
longitudinal, as in the other Leptosporangiates, although in
exceptional cases it may approach this position in Azolla.
From the epibasal half in the. latter arise, as in the other
Leptosporangiatae, the cotyledon and stem apex ; from the
hypobasal, foot and root. The quadrant walls do not always
arise simultaneously, but as soon as they are formed the
primary organs of the embryo are established and are arranged
in the same way as in other Ferns. Berggren ^ asserts that
the root does not develop until later, and is derived from the
foot ; but in sections it is very evident from the first, and
corresponds in position exactly with that of other Lepto-
sporangiates.

In all but the stem quadrant the octant walls are exactly
median, and this may be true of the latter ; but in the stem
quadrant the octant wall may make an acute angle with the
quadrant wall, and the larger of the two cells then forms at
once the two-sided apical cell of the stem, and from now on
divides alternately right and left. Where the octant wall is
median, it is probable, although this could not be positively
proved, that the stem apex forms for a short time three sets of
segments instead of two.

In the cotyledon the median octant wall is followed by a
vertical wall in each octant, forming two cells that appear
respectively triangular and four-sided. The former have lai^er

* Ber^ren (2), Figs. 4-16. « Bei^gren, /.r. p. 4.

LEPTOSPORANGIATM HETEROSPORE^

387

nuclei and divide for a time after the manner of two-sided
apical cells, and perhaps the first division of the leaf quadrant
may be of the nature of a true dichotomy, and these cells are
the apical cells of the two lobes. In the four-sided cell, the
radial and tangential divisions succeed each other with much

Fig. 199. — AzoUaJilicHloidts (Lam.). Development of the embryo, X350. A, B, C, Young embr>'OS
in median longitudinal section ; D, two horizontal sections of a young embryo ; £, three
transverse sections of a somewhat older one ; jr, x'^ initial cells of the cotyledon ; F, two longi-
tudinal sections of an advanced embryo ; G, horizontal section of an older one, with the rudiments
of the second and third leaves; 3, b^ ba§al wall of the embryo : */, stem ; L^, cotyledon ; r, root ;
A, hairs ; jr, apical cell of the stem ; L-, L', second and third leaves.

regularity. By the growth of the two initials (Fig. 199, E,
X, xf) the young cotyledon rapidly grows at its lateral margins
and bends forward so as to enclose the stem apex. At the
same time the upper marginal cells divide rapidly by ^ique

388 MOSSES AND FERNS chap.

walls alternately on the inner and outer sides, so that the
cotyledon also increases in length, and by this time it is about
four cells thick.

As soon as the apical cell of the stem is established, it grows
very much as in the mature sporophyte. Each segment divides
into a ventral and dorsal half, and each of these into an acro-
scopic and basiscopic portion. In case the stem octants are equal
at first it is not possible to say which is to form the stem apex,
but this is determined by the first division in each cell. One
of them divides by a vertical wall into equal parts and becomes
the second leaf ; the other forms the stem apex. If the octants
are unequal, the smaller one always forms the leaf At the base
of the cotyledon, between it and the stem, is a group of short
hairs (Fig. 199, F, h).

The primary root of Azolla arises in exactly the same way
as that of the typical homosporous Leptosporangiatae, except
that here the two root octants seem to be always equal in size,
and as practically only one of them forms the root, the other
dividing irregularly and becoming merged in the foot, the root
is more or less decidedly lateral (Fig. 199, E). After one
complete set of lateral segments has been formed, the primar}'
cap segment is cut off from the outer face, but, unlike the other
Ferns, this is the only one formed. The cap cell divides later
by periclinal walls, so that there are two layers of cells covering
the apical cell, and these are continuous with the epidermis of
the rest of the embryo, and continue to grow at the base, so that
a two-layered sheath is formed about the young root The
lateral segments are shallow and arranged very symmetrically,
and the divisions correspond to those in the other Ferns.

The divisions in the foot are more regular than is usually
the case, and this is especially noticeable in sections cut parallel
to the quadrant wall (Fig. 199, E). The general arrange-
ment of the cells is quite like that of the cotyledon, but the
divisions are fewer and the cells larger. Corresponding to
the upward growth of the cotyledon, the foot elongates down-
wards beyond the base of the root*, which thus appears as a
lateral growth from it, and no doubt led to Berggren's mistake
concerning its origin.

Salvinia in its early stages is much like Azolla^ but, according
to Leitgeb,^ the apical cell of the stem is always three-sided at
* Leitgeb, see Schenk's ** Handbuch der Botanik," vol. i. p, 216.

XII LEPTOSPORANGIAT^ HETEROSPORE.-E 389

first, and only later attains its permanent form. The root
remains undeveloped, and no later ones are produced, but the
first divisions in what corresponds to the root quadrant in Asolla
are apparently very similar to those of that plant, and it would
perhaps be more correct to say that the primary root remains
undeveloped rather than to consider it as completely absent.^

The second leaf in the embryo oiAzolla arises practically from
the first segment of the stem apex, and each subsequent
segment also produces a leaf. The early growth in length of
the primary root is slow, and it does not become conspicuous until
a late stage. The vascular bundles are poorly developed and
arise relatively late. No trace of them can be seen until the
second leaf is well advanced. Their origin and development cor-
respond to those in other forms described. The tracheary tissue
is composed entirely of small spiral tracheids.

The second root arises close to the base of the second leaf,
and like all the later ones is of superficial origin. As the
cotyledon grows, large intercellular spaces form in it, and the
young sporophyte breaks away from the spore or carries the
latter with it to the surface of the water. As the embryo breaks
through the episporic appendages at the top of the spore, these
are forced apart and the cap-shaped summit of the indusium is
thrown off. The cotyledon is funnel-shaped, with a cleft on one
side, and completely surrounds the stem apex. The root is still
conspicuous, and forms only a slight protuberance upon one side
of the foot, which looks like a short cylindrical stalk (Fig. 200).

The growth of the first root is limited, and it differs from the
later ones by forming peculiar stiff root-hairs. The later roots,
except the second,, do not seem to bear any definite relation
to the succeeding leaves.

A careful examination of the ripe macrosporangium shows
a number of colourless small round bodies occupying the space
between its upper wall and the indusium. These are the resting
cells of a nostoc-like alga — Anabcena AzoUcb, — which is always
found associated with this plant. At the same time that the
embryo begins to form, these cells become active, assume the
characteristic blue-green colour of the growing plant, and divide
into short filaments that at first look like short OscillaricB. The
cells soon become rounded, and heterocysts are formed. Some
of these filaments remain entangled about the stem apex of the

> Dutailly(i).

390

MOSSES AND FERNS

embryo, while others creep into special cavities which are found
in all the leaves except the cotyledon, and here develop into a
colony.

The first branch is formed after the plant has developed

Fig. 200. — Azolla filiculoides (Lam.). Nearly median section of the young sporophyte after it has
broken through the prothallium, x 100 : B, an older plant with the macrospore (i/) still attached ;
w, massuls attached to the base of the macrospore ; r, the primar>' root, x 45.

about eight leaves, but whether its position is constant was not
determined.

The Mature Sporophyte

Strasburger ^ has investigated very completely the tissues
of the mature sporophyte of Azolla^ and Prihgsheim - has done
the same in Salvinia, so that these points are very satisfactorily
understood.

The growing point of the stem in Azolla (Fig. 201, A) is
curved upward and backward, in Salvinia (Fig. 203, A) it is
nearly horizontal. In both genera there is a two-sided apical
cell from which segments arise right and left. Each segment
divides into a dorsal and ventral cell, and a transverse section
just back of the apex shows four cells arranged like quadrants
of a circle. In Azolla the dorsal cells develop the leaves, the
ventral ones the branches and roots. Each semi-segment is

* Strasburger (6).

Pringsheim (l).

LEPTOSPORANGIA T^ HETEROSPORE^

391

divided into an acroscopic and basiscopic cell, and these are further
divided into a dorsal and lateral cell in the upper ones, into a
ventral and lateral one in the lower. The leaves arise from one
of the dorsal cells, which may be either acroscopic or basiscopic,

■e

Fig. 90Z. — Azolla filiculoides iXAXSi.'). A, Vertical longitudinal section of the stem apex, x6oo; r,
mother cell of a root ; B, three successive transverse sections just back of the apex ; w, the
median wall ; L, mother cell of a leaf, x 600 ; C, single lobe of a young sterile leaf, X 600 ; D,
fertile leaf segments with two very young sporocarp rudiments, X 600 ; £, longitudinal section
of young macrosporangium, showing the young indusium (tr/)i X 600 ; /, first tapetal cell ; F,
older macrosporangium completely surrounded by the indusium,. X350 ; w, Anabctna filaments.

but is always constant on the same side of the shoot, so that
the two rows of leaves alternate. The lateral buds, which do
not seem to appear at definite intervals, arise from one of the

392 MOSSES AND FERNS chap.

upper cells of the ventral segment, and alternate with the leaves
on the same side of the stem.

The mother cell of a leaf is distinguished by its size and
position (Fig. 201, B, III, L), and the first division wall, as in
the cotyledon, divides it into two nearly equal lobes. No trace of
an apical cell can be found in the young leaf, and in this respect,
as well as the secondary divisions of the stem segments, AzoUa
differs from Salviniay where for a long time the young leaves
grow, as in most Ferns, by a two-sided apical cell (Fig. 203, A).
Each leaf lobe in Azolla is divided into an inner small cell and
an outer larger one, and the latter is then divided by a radial
wall. This formation of alternating tangential and radial walls

Fig. 202. — A, Young microsporangial sorus o^ A./iliculoides, x8o; col^ columella; iiL, industum ;
B, nearly ripe microsporangium, X 325.

is repeated with great regularity, and can be traced for a long
time. It is not unlike the arrangement of cells figured by Prantl ^
in some of the Hymenophyllaceae.

The fully - developed leaves of Azolla are all alike. In
A, filiculoides the two lobes are of nearly equal size, the lower
or ventral one, which is submersed, somewhat larger, but simpler
in structure. The dorsal lobe shows a large cavity near its base
(Fig. 204, A), which opens on the inner side by a small pore.
On the outer side the epidermal cells are produced into short
papillate hairs, which in some species, e,g. A, Carolintana, are
two-celled. Stomata of peculiar form (Fig. 204, B) occur on
1 Prantl (i), PI. I. Figs. 2, 3.

LEPTOSPORANGIAT^ HETEROSPORE^

393

both outer and inner surfaces. The bulk of the leaf is
composed of a sort of pah'sade parenchyma, and the cavity is
partly encircled by an extremely rudimentary vascular bundle.
The ventral lobe of the leaf is but one cell thick, except in the
middle, where there- is a line of lacunar mesophyll, traversed by
a simple vascular bundle.

In Salvinia the leaves are of two kinds. The dorsal ones
are undivided, and traversed by a single vascular bundle. The

Fig. 202'—SaJviHia natans (L.). A, Horizontal section of the stem apex, X450 ; L, young leaf; B,
a young leaf, showing the apical cell {x\ X450; C, longitudinal section of a segment of a
ventral leaf, X450; D, section of a dorsal leaf; r, lacunae; A, hair, X225 ; E, cross-section of the
stem, X 50 ; F, the vascular bundle, x 223.

mature leaf shows two layers of large air-chambers, separated
only by a single layer of cells, whose walls arc like those of the
epidermis. From both upper and lower surfaces, but especially
the former, numerous hairs develop. The ventral leaves are re-
peatedly divided, and each segment grows by a definite apical cell ;
the segments are long and root-like, and covered with numerous
long delicate hairs, looking like rhizoids. These submersed

394 MOSSES AND FERNS chap.

leaves doubtless replace the roots. The leaves in Salvinia are
arranged in alternating whorls of three, corresponding to the
nodes, and this arrangement accounts for the six rows of leaves
previously referred to.

The mature stem shows a central concentric vascular bundle
(Fig. 203, E, F), whose tracheary tissue is somewhat more com-
pact and the tracheae larger in Azolla, This is surrounded by
a definite endodermis and one or two layers of larger paren-
chyma cells, and radiating from the latter are plates of cells
separated by large air-spaces, and connecting the central tissue
with the epidermis (Fig. 203, E).

The lateral branches arise in acropetal order, but apparently
not always at equal intervals. Their development is a repetition
of that of the main axis. Like the branches, the roots in Azolla
arise acropetally, and their number is very much less than the
leaves. They arise from superficial cells and follow exactly in
their development the primary root of the embryo. The inner
layer of cells of the sheath, however, in these later roots be-
comes disorganised, and there is a space between this and the
root itself. A single root-cap segment only is formed subse-
quent to the primary one from which the sheath forms, and this
secondary cap segment undergoes division but once by periclinal
walls (Fig. 204, C).

Tlie Sporangia

The sporangia in both genera are contained in a so-called
sporocarp, which is really a highly-developed indusium. These
sporocarps always arise as outgrowths of the leaves, in Sahinia
from the submersed leaves, in Azolla from the ventral lobes. In
Salvinia several are formed together (Fig. 196, C), in Azolla
two, except in A, Nilotica^ where there are four. Elach
sporocarp represents the indusiate sorus of a homosporous
Fern.

In Azolla filiculoides these sori arise, as Strasburger ^ showed,
from the ventral lobe of the lowest leaf of a branch. My own
observations in regard to the origin differ slightly from his in
one respect. Instead of only a portion of the ventral lobe
going to form the sori, the whole lobe is devoted to the forma-
tion of these, and the involucre which surrounds them is the
reduced dorsal lobe of the leaf, and not part of the ventral one.
' Strasburger (6), p. 52.

LEPTOSPORANGIAT^ HETEROSPORE^

395

The leaf lobe, as soon as its first median division is complete,
at once begins to form the sporocarps, each half becoming
transferred directly into its initial cell. In this, walls are formed,
cutting off three series of segments (Fig. 201, D). Next a
ring-shaped projection arises about it, and this is the beginning
of the indusium {id) or sporocarp, which bears exactly the
same relation to the young sorus that it does in Trichomanes,
and Salvinia shows the same thing. From this point the two
sorts of sporocarps in Azolla differ. In the macrosporic ones
the apical cell develops directly into the single sporangium ; in

Fig. ixy^.—AzoUa JiliculoitUs (Lam.)- A, Longitudinal section of a dorsal lobe of the leaf, X about
40; », cavity with colony cX Attabetna; A, unicellular hairs; B, epidermis with stomata, X150
(after Strasburger) ; C, longitudinal section of young root, X325; sh, root-sheath.

the microsporic ones it forms the columella, from which the
microsporangia arise secondarily.

The ' development of the sporangia follows closely that of
the other Leptosporangiatae up to the final development of the
spores. The tapetum is composed of but a single layer of cells
in Azolla^ but in Salvinia it usually becomes double.^ In both

^ Juranyi (i).

396 MOSSES AND FERNS chap.

genera the wall remains single - layered, and . no trace of an
annulus can be detected.

In the macrosporangium of Azolla the archesporium pro-
duces eight sporogenous cells, the microsporangium sixteen.
In Salvinia^ according to Jur^nyi, both sporangia contain sixteen
spore mother cells.^ Shortly after the divisions are completed
in the central cell and tapetum the cell walls of the latter are
dissolved, but for a time the sporogenous cells remain together.
Finally, they become isolated and round off before the final
division into the young spores takes place. In the macro-
sporangium only one spore finally develops. This is at first,
in AsollUy a thin-walled oval cell lying free in the enlarged cavity
of the sporangium. Examination shows it to be surrounded by
a thick layer of densely granular nucleated protoplasm derived
from the tapetum. As the spore grows the surrounding proto-
plasm and the abortive spores are used by it as it develops, and
through their agency the curious episporic appendages of the
ripe spore are deposited upon the outside. The spore itself is
perfectly globular and surrounded by a firm yellowish exospore,
which in section is almost perfectly homogeneous. The epispore
covering this shows over most of the spore a series of thick
cylindrical papillae, from the top of which numerous fine thread-
like filaments extend. In section the epispore shows two
distinct parts, a central spongy-looking mass and an outer more
homogeneous part covering all but the tops of the papillae. At
the top of the spore are three episporic masses, composed entirely
of the spongy substance and surrounding a central conical mass
from whose summit extend numerous fine filaments like those
growing from the rest of the epispore. The name " swimming
apparatus," which has been applied to this apical mass, is a
misnomer, as the ripe sporangium sinks promptly when freed
from the plant.

The indusium rapidly grows above the young macrospor-
angium, or group of microsporangia, and its walls, which become
double, converge at the top and finally become completely
closed. In the former, before this happens, filaments oi Anabana
creep in and enter the resting condition. Thus they remain
until growth is resumed with the germination of the spore,
when the embryo is infected. The upper cells of the indusium
become very dark-coloured and hard, and remain after the lower
^ Hdnricher (2), however, states that there are but eight, as in AzoHa.

XII

LEPTOSPORANGIAT^ HETEROSPORE^

397

part decays.. The wall of the macrosporangium does not

Fig. 205. — Atolla filtculoides (Lam.). A, Mature sporophyte, X2; B, lower surface of a^lnich
with two microsporangial son (*/), x 6 ; C, macrosporangial (wr«) and microsporangial^;!;/)
Rori, xio.

become absorbed, as Strasburger^ states, but remains intact,
though very much compressed, until the spore is ripe.

' Strasburger (6), p. 71

398 MOSSES AND FERNS chap.

In the microsporic sorus, the apex of the placenta does not
develop sporangia, but remains as a sort of columella (Fig. 202, A).

The sporocarps of Salvinia are like those of Azolla, but the
two layers of cells are separated by a series of longitudinal air-
spaces which correspond to ridges upon the surface of the sporo-
carp (Fig. 1 96, D).

The microsporangia of Azolla have a long stalk, which
is composed of usually two, but sometimes three rows of
cells. The sixteen sporogenous cells all develop, so that
there are normally sixty-four microspores in each sporangium.
These have the exospore thin and smooth, and are included in
a kind of common epispore, which here too owes its origin
mainly to the tapetal cells. This episporic substance is divided
into masses (massulae), which have the foamy structure of the
episporic appendages of the macrospore. This appearance is
apparently due to the formation of vacuoles, which make these
massula! look as if composed of cells. The tapetal nuclei are
confined to the outside of the massulae, and can be detected
almost up to the time they are fully developed. Finally, upon
the outside of the massulae are formed the curious anchor-like
" glochidia " (Fig. 1 97, gt)^ whose flattened form is due to their
formation in the narrow spaces between the massulae.

In Salvinia the microsporangia arise as branches from
sporangiophores which bud out from the columella, so that their
number much exceeds that of the macrosporangia, or of the
microsporangia of Azolla, There are no separate massulae, and
in the macrosporangium the epispore is much less developed
than in Azolla,

The MarsiliacecB

The two genera of the Marsiliaceae, Marsilia and Pilularia,
are much more closely related than Salvinia and Azolla^ and at
the same time their resemblance to the homosporous Ferns is
closer, and of the two genera Pilularia is evidently the nearer to
the latter. The development of both gametophyte and sporo-
phyte in the two corresponds very closely.

The sporangia are borne in " sporocarps," which are morpho-
logically very different from those of the Salviniaceae, being
metamorphosed leaf segments enclosing several sori, and not
single sori enclosed simply in an indusium. The spores
germinate with extraordinary rapidity, especially in Marsilia,

LEPTOSPORANGIAT^ HETEROSPOREjE

399

and in M. Aigyptiaca the writer has found a two-celled embryo
developed within thirteen hours from the time the ungerminated
spores were placed in water.

The sporocarp of Marsilia is a bean-shaped body, which is
attached to the petiole of the leaf by a more or less prominent
pedicel. It is very hard, and unless opened artificially may
remain a long time unchanged, if placed in water ; but if a
little of the hard shell is cut away, the swelling of the interior
mucilaginous tissue quickly forces apart the two halves of the

Fig. 9c6.—Afarsilia vestita (Hook and Grev.). A, Fruiting plant of the natural Mze ; */,
sporocarps ; B, a single sporocarp, X 4 ; C, cross-section of the same, x 5 ; D, germinating
sporocarp, showing the gelatinous ring by which the sori {s) are carried out, x 3.

fruit. As more water is absorbed, this gelatinous inner tissue
continues to expand and forms a long worm-shaped body (Fig.
206, D), to which are attached a number of sori, each surrounded
by a sac-shaped indusium in which the sporangia are closely
packed. Macrosporangia and microsporangia occur in the
same sorus. The former contain a single large oval white
spore, the latter much more numerous small globular ones.
The indusium remains intact for several hours, if not injured.

400

MOSSES AND FERNS

CHAP.

but finally, with the sporangium wall, is completely dissolved,
and the spores set free.

The Microspores and Male Prothallium

The microspores of M, vestita (Fig. 207) are globular cells
about .075 mm. in diameter. The outer wall is colourless and

Fig. 207.— iT/ar«V/a vestita (Hook and Grev.). Germination of the microspores, X450; -«*,

ves^etative prothallial cell ; m, basal antheridial cell ; /, peripheral antheridial cells ; A, an

ungerminated spore, ventral aspect : B, section of a similar one — all longitudinal sections

except £ and F, which are transverse. In these the two groups of sperm cells are separated by a
large sterile cell.

sufficiently transparent to allow the contents to be dimly seen.
Lying close to the wall are numerous distinct starch granules,
and in the centre the nucleus is vaguely discernible. Sections
through the ungerminated spore show that the wall is thick,
with an inner cellulose endospore, outside of which are the

XII LEPTOSPORANGIAT^ HETEROSPORE.-E 401

exospore and the epispore or perinium, composed of closely-set
prismatic rods. The central nucleus is large and distinct, with
usually one or two nucleoli.

The first division takes place at ordinary temperatures,
about 20"" C, within about an hour after the spores are placed
in water. Previous to this the nucleus enlarges and moves to
one side of the spore, usually the point opposite the apex, and
the granular cytoplasm collects near the centre and is connected
with the peripheral cytoplasmic zone only by thin strands.
The first wall divides the spore into two very unequal cells, the
smaller containing but little granular contents, and representing
the vegetative part of the prothallium, while the upper becomes
the antheridium. In Pilularia there is subsequently cut off a
small cell from the vegetative cell, and Belajeff^ states that
this also is the case in Marsilia^ but a careful examination of
a great many microtome sections of M. vestita has failed to show
it in that species. The next division is not always the same, but
is usually effected by a wall nearly parallel to the first one, but
more or less concave, being in fact the homologue of the first
funnel-shaped wall in the antheridium of the Polypodiaceae (Fig.

207, D). Sometimes the antheridial cell divides at once by an
oblique wall into two nearly equal cells, from each of which
a group of sperm cells is later cut off. In no case was the
central cell cut off by a dome-shaped wall, such as is common
in the homosporous Ferns, and also in Pilularia, The forma-
tion of this wall is apparently suppressed here, perhaps as the
result of the extremely rapid development of the antheridium,
and the separation of the sperm cells takes place by walls cut
off from the periphery of the two upper cells. A cap cell (Fig.

208, d) is almost always present, as in Pilularia and the
Polypodiaceae.

From the two cells of the middle part of the antheridium
a varying number of sterile cells are cut off, which are quite
transparent, while the contents of the central cells are very
densely granular. Not infrequently the two groups of sperm
cells are completely separated by one of these sterile cells
(Fig. 207, F), but this is by no means always the case,
and does not justify Belajeff's^ interpretation of each group
representing a separate antheridium. It is simply a more
complete separation of the two primitive groups of sperm cells

1 Belajeff(3), p. 330. « Belajeff, /.f.

2 D

402

MOSSES AND FERNS

CUAP.

which is indicated by the first vertical wall in the central cell
of the antheridium of all Leptosporangiatae. The divisions in
the central cells are very regular, and the sixteen sperm cells in
each group are arranged very symmetrically (Fig. 208). The
whole number in M, vestita \s completed in about seven hours
from the time germination begins, and the formation of the sper-
matozoids commences about an hour later and takes about four
hours for its completion. The structure of the fully-developed
antheridium will be best understood from a comparison of the
three different views (Fig. 208, A, B, C). In these figures x

Fig. 208.— a, B, C, Sections made in three planes of the ripe antheridium of Marsilia vtstita^ X450 ;
J-, vegetative prothallial ceil ; //, cover cell of the antheridium ; D, E, spermatozoids, x 9CX) ; r.
the vesicle attached to the large posterior coils.

is the small vegetative cell, m the basal cell of the antheridium,/
the lateral wall cells, and <f the cover cell. Pilularia .approaches
much nearer to the Polypodiaceae in the structure of the
antheridium (Fig. 209). The first funnel-shaped wall is much
more frequently extended to the basal wall, and the two groups
of sperm cells are much less distinct than in Marsilia,

The spermatozoids of Marsilia are at once distinguished
by a great number of coils, sometimes thirteen or fourteen in
M, vestita. The cilia are very numerous, but are attached only

XII LEPTOSPORANGIATjE HETEROSPORE^ 403

to the broad lower coils, the upper narrow ones being quite
free from them, and, according to Strasburger,^ probably of
cytoplasmic nature — unfortunately the development of the
spermatozoids in Marsilia
is especially difficult to
trace. The vesicle at-
tached to the broad lower
coils is very conspicuous
and contains numerous
starch granules as well
as albuminous ones. In

Pilularia the long upper Fig. 209.-Ripc antherldium of Pilularia globnUfera

part of the SpermatOZOid <^>' ,*^°^« '^* ;^° vegetative prothalUal cells

\ ^ (jr, y\ X 375 ; B, free spermatozoid, showing the

is absent, and it apparently large vesicle (») with the contained starch granules.

corresponds only to the

few broad basal coils of that of Marsilia^ which are of nuclear

origin, like the greater part of the body in the spermatozoid of

Pilularia.

TJte Macrospore and Female Prothallium

The macrospores of the Marsiliaceae are extremely complex
in structure, and are borne singly in the sporangia. In Marsilia
vestita they are ellipsoidal cells about .425 x. 7 50 mm. in
diameter, ivory-white in colour, and covered with a shiny
mucilaginous coating. The upper part of the spore has a
hemispherical protuberance covered with a brown membrane,
and it is the protoplasm within this papilla that forms the
prothallium. The apex of the papilla shows the three radiating
ridges like those in the microspores, and indicates that, like
those, the macrospore is of the radial or tetrahedral type.

Sections of the ungerminated spore (Fig. 210, A) show a
structure much like that of the microspore, but more highly
developed. A noticeable difference is the segregation of the
protoplasm containing the nucleus, which occupies the apical
papilla. This is filled with fine granules, but is entirely free
from the very large starch grains of the large basal part of the
spore. The nucleus is somewhat flattened. A similar arrange-
ment of the spore contents is found in Pilularia, but the apex
of the spore does not form a distinct papilla. The epispore is
of nearly equal thickness, except at the extreme apex, in

' Strasburger (11), vol. iv. p. 122.

404

MOSSES AND FERNS

CHAP.

Marsilia^ but in Pilularia^ especially in P, globulifera, the
epispore of the upper third is much thicker, and from the
outside the spore appears somewhat constricted below this.

Previous to the first division, which in M. vestita takes
place about two hours after the spores are placed in water,
the amount of protoplasm at the apex increases, and the
nucleus becomes nearly globular and there is an increase in
the amount of chromatin. In Pilularia the first wall is always
transverse and separates the mother cell of the prothallium ;

Fig. 2IO. — Marsilia vestita (Hook and Grev.). Germination of the macrospore; A, longitudinal
section of the ripe macrospore, X 60 ; «, nucleus ; B-G, successive stages in the development of
the female prothallium and archegonium, X 360 ; C, £, transverse sections, the others longitudinal ;
H, neck canal cell ; A, ventral canal cell ; r, receptive spot of the egg ; A, remains of the^nucleiis
of the spore cavity.

but in Marsilia^ while this is usually so, occasionally a lateral
cell is cut off first from the papilla. In Pilularia the next wall
is parallel to this transverse primary wall, and this may also
occur in Marsilia, but in the latter more commonly the first
lateral cell is first cut off by a vertical wall, and this is followed
by two others, which intersect it and include a large central
cell (Fig. 210, E), from which a basal cell is subsequently
separated. In Pilularidy besides the formation of the basal cell
by the second wall, the central cell is, as a rule, cut out by two.

LEPTOSPORANGIAT^ HETEROSPORE^

405

and not three, walls. The basal cell of the archegonium in
Marsilia divides by cross-walls into equal quadrants, and the
lateral cells divide both by vertical and horizontal walls before
any further divisions take place in the archegonium. This
finally divides into the cover cell and inner cell. The neck is
very short, especially in Marsilia^ and each row has but two
cells. These in Pilularia (Fig. 211) are much longer. Both
neck and ventral canal cells are very small, especially in
Marsilia^ and the former has
Its nucleus undivided. In Mar-
silia the prothallium grows
gradually as the divisions pro-
ceed, but in Pilularia (Fig. 211)
the young prothallium increases
but little in size until the divi-
sions are almost completed, when
there is a sudden enlargement.
The complete development of
the prothallium occupies about
twelve to fifteen hours in Mar-
silia vestita, and in Pilularia
globulifera forty to forty -five
hours.

The egg in both genera is
large, but in Marsilia it is the
larger. In both, the receptive
spot is evident. The nucleus
is unusually small in Marsilia^
which otherwise resembles
Pilularia,

The phenomena of fecunda-
tion are very striking in the
Marsiliaceae. The mucilagin-
ous layer about the; macrospore attracts and retains the
spermatozoids, which collect by hundreds about it. . The
mucilage above the archegonium forms a deep funnel, which
becomes completely filled with the spermatozoids. As these
die their bodies become much stretched out, so that they
look very different from the active ones, with their closely
placed coils.. The attractive substance here is not confined
to the material sent out from the open archegonium, as the

Fig. ivx.^Pilularia globulifera (L-X A, B,
Young female prothalHa, longitudinal sec-
tions, X 300 ; c, neck canal cell ; C, section
of a recently fertilised archegonium, X 300 ;
sp^ spennatozoid within the egg.

4o6

MOSSES AND FERNS

CHAP.

spermatozoids collect in equal numbers about those which are
still closed, and even about spores that have not germinated
at all. Marsilia did not prove a good subject for studying
the behaviour of the spermatozoid within the egg, owing to
the difficulty of differentiating the spermatozoid after its
entrance. Pilularia is better in this respect, and shows that

Fig. 117.— Marsilia vestita (Hook and Grev.). Development of the embrya A, Loofptudinal
section of archegonium with two-celled embr>'o ; B, similar section of a later stage ; C, two
transverse sections of a young embryo ; D, two longitudinal sections of an older one : I, I, the
basal wall : L, cotyledon ; st^ stem ; r, root ; F, foot. A-C, x 525 ; D, x 360.

the changes are the same as those described in Marattia and
Osmunda,

Coincident with the first divisions in the embryo, each
of the lateral cells of the prothallium (venter) divides by a
periclinal wall, but the basal layer of cells remains but one cell
thick. The prothallium grows with the embryo for some

XII LEPTOSPORANGIAT^ HETEROSPORE^ 407

time, and in its later stages develops abundant chlorophyll,
and its basal superficial cells grow out into colourless rhizoids.
In case the archegonium is not fertilised, the prothallium grows
for a long time, and reaches considerable size, but never
develops any secondary archegonia. In PilulariUy both
prothallium and embryo may develop chlorophyll in perfect
darkness.^

The Embryo ^

The two genera correspond very closely in the development
of the embryo, which shows the greatest resemblance to the
Polypodiaceae. In Marsilia the development of the embryo
proceeds very rapidly. The first division of the egg is com-
pleted within about an hour after the spermatozoid enters,
and in Pilularia after about three hours, as nearly as could
be made out. In both the basal wall is vertical and divides
the somewhat flattened egg exactly as in Onoclea, The quad-
rant walls next follow, and then the octant walls, as usual.
Of the latter the one in the root quadrant diverges very strongly
from the median line (Fig. 212, C), and that in the foot quad-
rant is much like it. In the others it is nearly or quite median,
and it is impossible to say which of the leaf and stem octants
is to form the apical cell of those organs. The relative posi-
tion of the young organs is exactly the same, both with
reference to each other and to the archegonium, as in the
Polypodiaceae.

Tlie Cotyledon

The cotyledon grows for a time from the regular divisions
of one or both of the primary octant cells, but this does not
usually continue long, and the subsequent growth is purely
basal. The cotyledon is alike in both genera, and is a slender
cylindrical leaf tapering to a fine point, where the cells are
much elongated and almost colourless. Its growth is at first
slow, but at a later period (in Pilularia globulifera about the
eighth day) it begins to grow with great rapidity and soon
reaches its full size. This is largely due to a simple elongation
and expansion of the cells, which are separated in places, and
form a series of longitudinal air-channels separated by radiating
plates of tissue (Fig. 213, i). The simple vascular bundle

* Arcangeli (i), p. 336. ^ Hanstein (2).

4o8

MOSSES AND FERNS

traversing the centre is Concentric, with a definite endodermis,
but the tracheary^ tissue is very slightly developed. This
becomes first visible about the time the leaf breaks through the
calyptra.

The Stem

Of the two octants in the stem quadrant one becomes at
once the apical cell of the stem, the other the second leaf,
as in other Leptosporangiatae. The first wall in each octant
meets octant and quadrant walls, and cuts off a large cell

Fig. 313. — Longitudinal section of the young sporophyte of Piluiaria glohuli/era, still enclosed in
the calyptra {cat), and attached to the macrospore (j/), x 75 ; B, the lower part of the s.ame
embryo, X 215 ; r, apical cell of the root ; */, apical cell of the stem ; /, lacunz.

from each octant, in contact with the foot. Hanstein and
Arcangeli regard these as part of the foot, and physiologically
they no doubt are to be so considered, but morphologically they
are beyond question segments respectively of the stem and second
leaf. At first these are not distinguishable from each other, but
the divisions in the latter are usually (in Piluiaria) less regular,
and the apical cell early lost. It may, however, develop a
regular three -sided apical cell, like that of the later leaves.
The earlier segments of the stem apex are larger than the
subsequent ones, and the broadly tetrahedral form of the

XII LEPTOSPORANGIATAH HETEROSPORE^ 409

primary octant is reduced to the much narrower form found
in the older sporophyte.

The Root

The 'first wall in the root quadrant strikes the basal wall
at an angle of about 60°, so that the octants are of very
unequal size (Fig. 212, C), and the larger one, as in other
similar cases, becomes at once the initial cell of the root, which
in both genera shows the same regular divisions that char-
acterise the Polypodiaceae. The segments of the root-cap do
not form any periclinal walls, and remain single-layered. The
root, like the cotyledon, is traversed by regular air-chambers,
and its transverse section resembles very closely that of the
leaf. These air-chambers appear while the root is very young,
and at a point between the endodermis and the cortex. The
latter is at this stage divided into But two cells, the outermost
of which by a further tangential division becomes two-layered,
the outer forming the epidermis, and the inner by similar
divisions three-layered. The two outer layers divide by radial^
walls, but the inner ones divide only by periclinal walls, and
form one-layered lamellae separating the air-spaces and connect-
ing the endodermis with the outer cortex.

The Foot

The first divisions in the foot quadrant follow closely those
in the root, but this regularity soon ceases, and after the first
divisions no definite succession in the walls can be distinguished.
The foot remains small, but, as we have seen, the first segments
of the lower epibasal octants practically form part of it, and
doubtless all the lower cells are concerned in the absorption of
food from the spore. The volume of the protoplasm in the
spore increases as the . prothallium grows, but loses more and
more its coarsely granular structure. In both Marsilia and
Pilularia the nucleus of the spore cavity soon becomes indis-
tinguishable, and in the former is from the first very small. In
Pilularia it is larger, and in the later stages bodies were
observed that looked as if they might be secondary " endosperm-
nuclei," like those of Azollay but their nature was doubtful.

The leaves are at first alike in both genera, and the earliest
ones do not show any trace of the circinate vernation of the

410 MOSSES AND FERNS chap.

later ones. In Pilularia the later leaves are essentially like the
cotyledon, but in Marsilia all the later leaves show a distinct
lamina. This is at first narrow and undivided, and spatulate
in form. In M. vestita this is succeeded by five or six similar
ones, with constantly-broadening laminae, which finally divide
into two narrow wedge-shaped lobes, and these are then
succeeded by others with broader lobes, which finally are
replaced by four lobes, the central ones being narrower than
the outer ones. All of these early lobed leaves are folded flat,
and it is not until about ten or twelve leaves have been formed
that finally the leaf attains the form and vernation of the fully-
developed ones.

The divisions in the stem apex take place slowly, but
apparently a complete series of segments is produced in rapid
succession, and there is an interval before any more divisions
occur, as there is always considerable difference in the ages of
any two succeeding sets of segments. The apical cell of
Piltdaria in cross-section has the form of an isosceles triangle
with the shorter face below. Probably each dorsal segment at
first gives rise to a leaf, and each ventral one to a root How-
ever, the number of roots exceeds that of the leaves, but the
origin of these secondary roots was not further investigated.

Tlu Mature Sporophyte

In both Marsilia and Pilularia the fully-developed sporo-
phyte is a creeping slender rhizome, showing distinct nodes and
intemodes. At the nodes are borne the various appendages of
the stem, and the elongated internodes are, except for occasional
roots, quite destitute of appendages. Leaves and branches
arise from the nodes, and in Marsilia are much crowded. The
plants are aquatic or amphibious, and the habit of the plant is
very different, especially in Marsilia^ as it grows completely
submerged, or partially or entirely out of water. Some species,
like M. vestita^ which grow where there is a marked dry season,
grow in shallow ponds or pools, which dry up as the end of the
growing period scpproaches, and the ripening of the sporocarps
takes place after the water has evaporated. In the first case
the petioles are extremely long and weak, and the leaf-segments
float upon the surface. In the other case the petioles are much
shorter and stouter, and the leaves are borne upright The

LEPTOSPORANGIAT^ HETEROSPORE^

411

young leaves are circinate, as in the ordinary Ferns, and in

Fig. 214.— Part of a fruiting plant oi Pilularia Americana (A. Br.), X4 : */, sporocarps.

412

MOSSES AND FERNS

CHAP.

Pilularia retain the same structure as the cotyledon. In
Marsilia they are always four-lobed. The sporocarps are
modified outgrowths of the petiole, which are often formed so
near the base as to appear to grow directly from the stem.
They often are borne singly, but may occur in considerable
numbers — twenty or more in M. polycarpa — and are globular
in PilulariUy bean-shaped in Marsilia, The growth of the

Fig. 21$.— Marsilia vestita (Hook and Grcv.). A, Vertical longitudinal section of the stem apex,
x8o ; L, leaves ; tU stem apex ; r, roots ; B, the stem apex, X450 ; C, horizontal section of rvry
young leafr X 450 ; D, similar section of an older one, x 450 ; £, cross-section of mature stem,
x8o.

Stem and the origin of the various appendages are the same in
both genera.

A longitudinal section of the stem (Fig. 215, A) shows the
decidedly pointed apex occupied by a large and deep apical
cell with very regular segmentations. Each segment divides
into an inner and an outer cell, the former in all the segments
forming the central plerome cylinder, and the outer cells
developing the cortex of the stem, and the leaves in the dorsal
segments, the roots in the ventral ones. The young leaves are

XII LEPTOSPORANGIAT^ HETEROSPORE^ 413

separated by distinct intervals or internodes, and apparently
all of the dorsal segments do not give rise to leaves, but just
what the relation is between the nodes and internodes was not
determined. The roots arise in strictly acropetal order from
the ventral segments, but their number does not seem to be
constant. In Pilularia Americana the number of roots con-
siderably exceeds that of the leaves, as it does in the young
sporophyte of P, globulifera.

The siiigle axial vascular bundle is truly cauline, and
extends considerably beyond the base of the youngest leaf.
The later leaves in Pilularia^ both in their growth and complete
structure, correspond to the primary ones. They grow for a
time from a three-sided apical cell, in which respect they differ
from Marsilta, The development of the leaf of the latter has
been carefully studied by Hanstein in M, Drummondii^ and M,
vestita corresponds exactly with that species. A section of the
very young leaf (Fig. 215, C) parallel with the surface shows
a large two-sided apical cell. The leaf- rudiment assumes a
somewhat spatulate form, and on either side a projecting lobe
is formed, the rudiment of one of the lateral segments of the
leaf. The apical cell is now divided by a median wall, after
which periclinal walls are formed, and from this time the growth
of the leaf can no longer be traced to a single initial cell. The
first longitudinal wall in the apical cell establishes the two
terminal lobes, which at first are not separated (Fig. 215, D).
The establishment of the veins follows exactly as in Ferns with
a similar venation, and is strictly dichotomous. The stem
branches freely in both genera, and the branches arise close to
the apex, and below a young leaf somewhat as in Azolla,

The roots correspond exactly with those of the higher
homosporous Ferns. The segmentation of the apical cell
follows the same order as in the Polypodiaceae. Goebel's figure
of M. salvatrix^ differs somewhat from the account given more
recently by Andrews ^ for M, quadrifolia. The latter observer
states that there are no periclinal walls in the root-cap segments,
which remain throughout one-layered, and that the separation
of the plerome takes place earlier than Goebel indicates. Van
Tieghem's* account of the root of M. Drummondii confirms
Andrews' observations upon M, quadrifolia. The bundle of the
root is diarch, as in the Polypodiaceae, and the lateral roots arise

^ Goebel (10), p. 238. * Andrews (i). ' Van Tieghem (5), p. 535.

414 MOSSES AND FERNS chap.

in the same manner. The endodermal cells from which they
spring are distinguished from the others by their shorter and
broader form, and are very easily recognisable by this as well as
from their position. They form two vertical rows exactly opposite
the ends of the xylem plate, and the lateral roots therefore
are also strictly two-ranked. Narrow lacunae are formed in the
cortical tissue of the root, and the cells surrounding these are
connected by regular series of short outgrowths, which connect
them in a way that recalls very strongly the connecting tubes
between conjugating filaments of Spirogyra, and produce a
similar ladder-shaped appearance.

The solid vascular cylinder of the young stem is later
usually replaced by a tubular one, but its structure is also
concentric, with phloem completely surrounding the xylem, and
has both an inner and outer endodermis. When the plants are
completely submerged the ground tissue is mainly parenchyma,
but in the terrestrial forms sclerenchyma may be developed in
the cortex of the stem and petiole. The latter is always
traversed by a single axial bundle, which in the lamina in
Marsilia divides repeatedly near the base of the wedge-shaped
leaflets into numerous dichotomous branches.

Luerssen ^ mentions as special reproductive bodies, tubers
found in M, hirsuta. These are irregular side branches covered
with imperfectly-developed leaves, and with the cortical tissue
strongly developed and full of starch. These are supposed to
survive long periods of drought, and to germinate under favour-
able conditions. A condition somewhat analogous to this
appears in M, vestita (Fig. 206, A), but whether these short
lateral branches are of this nature was not investis^ated.

.*^CJ

Tlie Sporocarp^

The development is much the same in the two genera, but
is most easily followed in the simple sporocarp of Ptlularta, In
P, Americana^ the young fruit begins to develop almost as soon
as the leaf can be recognised, and while it is still close to the
stem apex. Growth is stronger upon the back of the young
leaf, and it very early assumes the circinate form. Before this

^ Luerssen (7), p. 601.

' Sachs, Text-book, 2nd English edition, p. 455; Goebel (6); Juran)*i (2);
Russow (i), Meunier (i).

LEPTOSPORANGIAT^ HETEROSPOREAi

415

curvature is very pronounced, however, in the sporophyll, a
protuberance arises upon its inner face, a short distance above
the base (Fig. 216, A). This originates from a single cell,
which functions for some time as an apical cell, and causes the
young sporocarp to project strongly from the leaf, of which it
is simply a branch, somewhat analogous to the spike in
Ophioglossum, It has at first the form of a blunt cone, but
soon upon the side turned toward the leaf a slight prominence
appears (Fig. 216, B, L), and about the same time two similar

Fig. ^16.— Piiularia Americana (A. Br.X Development of the sporocarp. A, Very young
sporophyll with sporocarp rudiment (x/), showing a distinct apical cell ; B-D, longitudinal
sections of young stages, showing the formation of the "sorus canals" {sc\ XX30; 7% the
original apex of the j^oung sporocarp ; L, secondary lobes or leaflets ; E, longitudinal section of
an older stage, x about 130; s, s, young sori ; F, transverse section of an older sorus, x 180.

lateral ones are formed. As in the sterile part of the leaf growth
is stronger on the outside, and the young sporocarp bends in
toward the leaf, so that the position of fertile and sterile
segments is very like that in the young sporophyll of Ophio-
glossum. The apex of the sporocarp rudiment, together with
the three lobes, enclose a slightly depressed area, which
becomes the top of the sporocarp. The four prominences
(including the original apex of the fertile segment) are beyond

4i6 MOSSES AND FERNS chap.

question to be considered leaflets, which remain confluent
except at the top. A little later a slight depression or pit
forms at the base of each lobe and the central area at the top.
These pits are separated laterally by the coherent edges of the
leaflets, which extend to the axis of the sporocarp and are
continuous with it. As the young fruit enlarges, the depres-
sions deepen owing to the elongation of both leaflets and the
axial tissue, which forms a sort of central columella (Fig. 216,
D). Thus are formed four deep cavities, separated laterally by
the united margins of the leaflets, and corresponding to the
much more numerous "canals" described by Russow in the
fruit of Marsilia ; like these they at first open at the summit by
a pore, and a study of longitudinal sections shows clearly
their strictly external origin.

Up to the time the cavities begin to form, the young fruit
is composed of uniform tissue, but shortly after, the tissue
systems become differentiated, and the peduncle of the sporo-
carp is formed. At this time the vascular bundle of the
peduncle can be recognised, and joins that of the sterile
segment near its base. The peduncle is much longer in P.
Americana than in the very similar P, globulifera. The
circinate coiling of the sterile segment is repeated, though less
conspicuously, here, and the body of the sporocarp is bent at
right angles to the peduncle.

The cavities rapidly become larger with the expansion of
the growing sporocarp, but the space between the inner surface
of the lobes and the columella remains narrow, owing to the
growth of the sorus, which almost completely fills it from the
first. The sorus forms an elongated cushion, extending nearly
the whole distance from the apex to the base of the lobe, along
the median line of its inner face. In origin and position it
corresponds exactly to that of most homosporous Ferns, except
that it arises from the upper instead of the lower side of the
leaf. The laminae separating the cavities are composed of
about four layers of cells.

The vascular bundle of the peduncle divides into four
branches, where it enters the sporocarp, and one branch goes
to each lobe, of which it forms the midrib lying below the
sorus. From each of these, two smaller branches are given
off* near the base, following the margin of the lobe (Fig,
217, A). By this time the outer epidermal cells begin to

LEPTOSPORANGIAT^ HETEROSPORE^

417

thicken, the first indication of the hard shell found in the ripe
sporocarp.

The development of the sporangia corresponds almost
exactly with that of the Polypodiaceae. The surface cells of
the sorus protrude as papillae, in which the same divisions arise
as in other Leptosporangiatae. The first division wall is
usually strongly oblique, but may be transverse. The formation
of the archesporium is the same, but the apical growth of the

Fig. 217. — ^Transverse section of an older sporocarp of/*. Americana, showing the four sori (*);
/bf vascular bundles, x 85 ; B, section of the wall of a nearly ripe sporocarp, x 955.

sporangia is checked sooner in the earlier ones, which have
consequently a very short stalk. In the later ones, which arise
between the others, the stalk is longer. The first sporangia are
formed at the base of the sorus, and their development
proceeds toward the apex ; but later secondary ones may arise
at any point in the sorus.

The tapetum is well developed, and, as in most homosporous

2 E

4i8 MOSSES AND FERNS chap.

Ferns, consists of two layers, in some places of three. The
number of sporogenous cells is usually eight, but some or all of
these may divide again, so that the whole number ranges from
eight to sixteen. The dissolution of the tapetum walls and
subsequent division of the spores follow precisely as in AzoUa.
In stained sections the nucleated protoplasm of the tapetal cells
is very evident after the walls have disappeared. At this point
the difference in the two kinds of sporangia becomes manifest
Those in the lower part of the sorus, i,e, the oldest ones, form
the macrosporangia, the upper ones microsporangia. In the
latter all the spores mature ; in the former, as in Azolla^ one
spore grows at the expense of the other, and finally fills the
sporangium completely. As in Azolla no trace of an annulus
is seen, either in the young or fully-developed sporangium.^

As the sporocarp ripens, the outer cells become excessively
hard, especially the first layer of hypodermal cells (Fig. 2 1 7),
whose walls become so thick as to almost obliterate the cell
cavity. The second hypodermal layer is also thickened, but not
so strongly. At maturity the sporocarp of P, Americana forms
a globular body about 3 mm. in diameter, covered with
hairs, and attached to a long peduncle which bends downward
and buries the ripe sporocarp more or less completely in the
earth. The statement ^ that this species has but three
chambers is incorrect, and except for the longer pedicel of the
fruit, and a slightly thinner epispore in the upper part of the
macrospore, it corresponds exactly to P, globulifera. The
sporocarp splits into four parts, corresponding to the four lobes
of the young fruit, and the membranaceous margins of the leaf
form a tough indusium surrounding the sporangia. This
indusium is not, at least in P. globuliferay readily pervious to
water, and germination does not begin for a long time after the
valves separate, unless the indusium is artificially opened.
Except for the number and position of the sori, and the relative
position of the two sorts of sporangia, Marsilia agrees exactly
with Pilularia, The sorus canals form two longitudinal rows
along the sides of the elongated fruit rudiment, which may be
compared to a pinnate leaf. In Marsilia^ occupying the middle

* For the details of the development of the macrospore, see Meunier (1), ppu

382.387.

* Goebel (10), p. 240 ; Underwood (4), 2nd ed., p. 127 ; ** Botany of California,"
vol. ii. p. 352.

XII LEPTOSPORANGIAT^ HETEROSPORE^ 419

line of each sorus, is a row of large tetrahedral cells, which form
three sets of segments, like any three-sided apical cell. Each of
these cells produces a group of sporangia. The terminal one,
derived directly from the apical cell, is a macrosporangium ; the
smaller lateral ones, derived from its earlier segments, the
microsporangia.

Fossil Leptosporangiate

Sporangia of undoubted Leptosporangiatae are exceedingly
rare in the earlier geological formations. Solms-Laubach ^
cites Hymenophyllites as probably being a genuine leptospor-
angiate Fern, and Zeiller^ describes some isolated sporangia
that seem to be much like those of the modem Gleicheniaceae.
Forms like the Osmundaceae have also been described by
various writers, but no traces of Cyatheaceai or Polypodiaceae
have been yet detected in Palaeozoic formations. In the
Jurassic, undoubted evidences of Gleicheniaceae, Osmundaceae,
and Schizaeaceae are found,' but the Polypodiaceae do not
seem to have appeared until still later. The existence of the
Hydropterides below the Tertiary is doubtful, but in the latter
formation occur undoubted remains of the living genera
Salvinia, Pilularia^ and Marstlia.

^* Affinities of the Leptosporangiatce

The Osmundaceae undoubtedly are intermediate between
the Eusporangiatae and Leptosporangiatae, but with which
order of the former their affinities are closest is difficult to say.
Among the Ophioglossaceae, the larger species of Botrychium
and Helminthostachys show apparent close structural similarity ;
but, on the other hand, in the distinctly circinate leaves and
the character of the sporangia, as well as the histology, the
Marattiaceae are certainly quite as nearly related. Apparently
all of these forms are generalised types, springing from a
common stock, but no two of them directly related.

Among the Leptosporangiatae themselves the relationships
are evidently much closer. A common type of prothallium and
sporangium prevails throughout, even in the heterosporous forms.
The four families, Osmundaceae, Gleicheniaceae, Cyatheaceae, and

* Solms-Laubach (2). ' 2^1er (i); Bower (12), p. 126. » Radborski (i).

420 MOSSES AND FERNS chap.

Polypodiaceae, form a pretty continuous series, of which the
Polypodiaceae are with very little question the latest and most
specialised forms. This is evinced both by the geological record,
which, so far as yet examined, shows that they were the latest
to appear, and by the fact that at present they greatly out-
number the other Ferns, probably including at least 90 per
cent of all living species. The single genus Polypodium has
over 400 species, probably as many as all the lower Ferns
combined. These facts, together with the specialised character
of all the parts, indicate that they are Ferns which have adapted
themselves to modern conditions.

The Schizaeaceae and Hymenophyllaceae do not seem to
belong to this main line, but are somewhat peculiar types,
apparently belonging near the bottom of the series. The
Hymenophyllaceae, on the whole, approach most nearly the
Gleicheniaceae, with which they agree in many points, both in
the sporophyte and gametophyte, but they also recall the
Osmundaceae, and possibly may form a branch somewhere
between the two, but nearer the former. The peculiarities of
the gametophyte are probably in large measure the result of
environment, and the filamentous prothallium of some species
of Trichomanes is beyond question a secondary and not a
primary condition, and the prothallium is typically like that of
the other Leptosporangiata^.

The nearest affinities of the Schizaeaceae seem to be with
the Osmundaceae, but in the structure and arrangement of their
vascular bundles they are more like the Gleicheniaceae.

Of the two families of the Hydropterides, the Salviniaceae
show several points of resemblance to the Hymenophyllaceae.
The development of the leaves is strikingly like those of
Hymenophyllaceae, with reniform or palmate leaves, and the
structure of the sori almost identical. The absence of second-
ary roots in Salvinia is suggestive also of the similar absence
in some species of Trichomanes, The two-sided apical cell of
the stem is, however, different from that of the few Hymeno-
phyllaceae examined, which all possess the pyramidal initial,
but possibly further examination may show forms with an
initial cell similar to that of Azolla or Salvinia.

The Marsiliaceae in all respects, except their heterospory,
conform closely to the type of the higher families, and may be
assumed to be derived directly from the Polypodiaceae, or forms

XII

LEPTOSPORANGIA T^ HETEROSPORE^

421

much like them. The curious Ceratopteris suggests a possible
connecting form. This strictly aquatic Fern has the large
sporangia with the ahnulus sometimes incomplete, and the
sporophylls modified into pod-like structures which suggest a
possible homology with the " fruit " of the Marsiliaceae. The
form of the early leaves, too, suggests those of Marsilia, The
two genera of the Marsiliaceae are evidently very closely
related, and of these Pilularia approaches nearer the homo-
sporous Ferns. The accompanying diagram shows the
relationship assumed here.

Azotla

EMsporangiaia

CHAPTER XIII

EQUISETINE^E

All of the living representatives of the second class of the
PteridopRytes may without hesitation be referred to the single
genus Equisetum^ with about twenty-five species, some of which,
e^, E. arvensCy are almost cosmopolitan. In the largest species,
E. giganteufHy the stems reach a height of i o metres or more,
but are slender, not more than 2 to 3 cm/ in diameter,
and supported by the surrounding trees and bushes. The
smallest species is E, scirpoides (Fig. 242, B), whose slender
stems are seldom more than 1 5 to 20 cm. in length, and often
one millimetre or less in diameter. In spite of these differences
in size, the structure is remarkably uniform, both in gameto-
phyte and sporophyte. The following account is based mainly
upon a study of E, telmateia} but applies to the other species
that have been studied.

The Prot/uzllium

The ripe spore of Equisetuni is globular and shows no
trace of the ventral ridges usually evident in tetrahedral spores.
Four distinct membranes surround it, the inner one (intine)
being exceedingly delicate, but with care showing the cellulose
reaction.^ Outside of this are the exospore and the elaters,
between which lies another layer, " Mittelhaut " of Strasburger,'
belonging to the exospore. The well-known elaters (Fig. 218,
A) form two strips attached in the middle and terminating in
spoon-shaped appendages. The elaters are usually more or
less spirally twisted, and when dry show faint oblique striations,

* E, maximum. ' Buchtien (1).

® Strasburger, ** Bau und Wachsthum der Zellhaute," p. 199.

CHAP. XIII

EQUISETINE^

423

except on the expanded ends. They are extremely hygroscopic,
and respond instantly to any changes in the moisture of the
atmosphere. A careful study of the dehiscence of the spor-
angium shows that as it dries the expansion of the elaters
assists very materially in opening it, and their function is
something more than that of keeping the spores together, as
has been asserted.^ The striation of the elaters is merely the
result of wrinkling by drying, and when moistened this dis-
appears completely. The elaters show the cellulose reaction
except upon the upper surface, >vhich is cuticularised.

The spores contain much chlorophyll, which in the dry
spores appears amorphous and gives them a dark olive-green
colour. So soon as the spor^ is moistened, however, it increases

Fig. 218.— In this and all the following figures of EgMtsetum, the drawings were made from E. tel-
maieia (£hrh.X {E. maximum^ Lam.)* unless otherwise indicated. A, ripe dry spore with
expanded elaters, X 180 ; B, a similar spore placed in water, X 180 ; C, D, germinating spores,
X360 : E, older stages of germination, X x8o ; r, primary rhizoid.

in diameter by about one-half through the absorption of water,
and the numerous small round chloroplasts then become very
evident. The nucleus is large, and occupies the centre of the
spore. After a short time the elaters and the outer layer of
the exospore are thrown off, and probably the rest of the
exospore, as no trace of this can be seen in the young
prothallium.

The spores quickly lose their power of germination, and
should be sown as soon as they are discharged. If this is done
germination begins almost at once, and within ten to twelve
hours the first division wall may be completed. The chloro-
plasts rapidly multiply by division and often show a distinct

^ Buchtien (i), p. 15.

424 MOSSES AND FERNS chap.

radiae arrangement, extending in lines from the nucleus to the
periphery. The first division may occur before the spore has
changed form, and in this case (Fig. 2 1 8, C) a small cell is cut
oflT by a strongly curved wall. Both cells contain chlorophyll,
but the nucleus of the smaller cell is smaller than the other.
In other spores there is first an elongation, as in Osmunda, and
the smaller end, which like that has some chlorophyll, but not
so much relatively as the larger, is cut off, and forms the first
rhizoid, and within twenty-four hours, under suitable conditions,
this may reach a length considerably exceeding the diameter

Fig. 2x9. — Young prothallia of Equisttum^ showing the variation in form, Xi8a In A there is
apparently a definite initial cell ; r, rhizoid.

of the spore. Sadebeck^ showed and Buchtien^ confirmed
this, that the first root-hair is positively heliotropic.

The first divisions in the prothallial cell are extremely
various, in this recalling the behaviour of the eusporangiate
Filicineae and the Osmundaceae. The first wall may be either
vertical or transverse (Fig. 2 1 8), and sometimes, but not often,
there are several transverse walls, and a short filament is formed.
More commonly the first transverse wall is followed by a
vertical wall in one or both cells. In case the first wall is
vertical it not infrequently happens that the two cells, by
repeated transverse divisions, form two parallel rows of cells,
which may diverge, so that the young prothallium becomes two-
* Sadebeck (6), p. 177. ^ Buchtien (i), p. 29.

EQUISETINE^

425

lobed. In a number of cases a two-sided apical cell was seen
(Fig. 219), but its growth is very limited. Finally, a cell-mass
occasionally is the first product of germination. As a not
infrequent occurrence may be mentioned also the suppression of
the first rhizoid (Fig. 2 1 9, C). The development for some time
is so varied that it is impossible to give any rule for it, but
generally the prothallium at this stage, like that of the lepto-
sporangiate Ferns, consists of but one layer of cells, and does
not show a midrib. These prothallia also do not have a
definite apical growth, and are usually more or less branched.
Often, however, the prothallium while still small has a some-

FiG. a/a— A, Female prothallium with the first archegonium («r), x 70 ; B, male prothallium, x 70.

what cylindrical body composed of several layers of cells, and
in these the root-hairs are mainly confined to the base. The
chloroplasts which these at first contain are gradually changed
into leucoplasts, and may be completed absorbed.^

Ttie Sexual Organs

The prothallia of Equisetum are usually dioecious, and, as is
usual in such cases, the males are smaller and the antheridia
develop first. The latter generally appear in about a month.
In -£. telmateia there is not so much difference in the appear-

' Buchticn (i), p. 17.

426

MOSSES AND FERNS

CHAP.

ance and size of the male and female plants, and they are
not always distinguishable by the naked eye. While in this
species, as in others, the antheridia may form at the ends
of the prothallial branches, they also may be formed upon
a meristem quite like the archegonia, and are usually in
this species in groups, so that longitudinal sections show
antheridia of very different ages, all evidently derived from the
activity of the meristem (Fig. 221). The development shows
a close resemblance to that of the eusporangiate Ferns, and
in connection with the other points in the growth of the
gametophyte and sexual organs, suggest a nearer 'connection of
these two groups than is usually admitted. Here, as in the

Fig. mi.— Development of the antheridium, X 190. A, Longitudinal section through the aniheridial
meristem showing antheridia of diflferent ages ; B, longitudinal section of young antheridtnm,
X 375 ! Ci t^o sections of a terminal, single antheridium, nearly pp^i X 190 ; D, three
transverse sections of young antheridium, X 190 ; o, opercular cell.

eusporangiate Ferns, the antheridium mother cell is divided
into an inner and an outer cell, of which the inner one forms at
once the sperm cells. When the antheridium arises at the end
of a filament, the divisions in the terminal cell are very much
like those in Osmunda. In the mother cell three intersecting
walls enclose a tetrahedral cell, which then has the cover cell
cut off by a periclinal wall. In both forms of antheridfUm the
subsequent history is the same. The central cell divides first
by a transverse wall, followed by vertical walls in each cell, and
subsequently by numerous divisions which show no definite
arrangement (Fig. 221, C), and produce a very large number of
sperm cells. In the cover cell only radial walls are formed, and

XIII

EQUISETINE^

427

it thus remains single-layered, as in Marattia and Osmunda,
There is often a triangular opercular cell (Fig. 221, D, o\ re-
calling the similar cell in these forms.

Development of the Spermatozoids

The large size of the spermatozoids of Equisetum makes
them especially suitable for the study of their development, and
this was traced with some care in E, telmateia. The material

Fig. 333. — Development of the spermatozoids, x zooo. A, Three of the central cells of an antheridium
before the final division ; B-E, final nuclear divisions in the sperm cells ; F-J, development of
the spermatozoid from the nucleus of the sperm cell ; r, the cilia ; K, two free spermatozoids ; v,
the vesicle.

used was fixed with i per cent chromic acid, stained with alum-
cochineal, and microtome sections were then examined in Canada
balsam. The nuclei of the sperm cells previous to their final
division are globular and show one, sometimes two, small but dis-
tinct nucleoli, and numerous chromosomes. In exceptional cases
the two " directive spheres " could also be seen. Previous to
the final division the latter take their place on opposite sides of
the now somewhat flattened nucleus, whose nucleolus cannot be
distinguished and whose nuclear segments are very distinct,

428 MOSSES AND FERNS chap.

short, curved bodies. Their number could not with certainty
be determined. The nucleus passes through the various
karyokinetic phases, and the directive spheres occupy the poles
of the nucleus spindle when at a later period they divide so
that each daughter nucleus has two of them. After the
daughter nuclei have assumed the resting condition these can
no longer be distinguished, and what their fate is must for
the present remain undecided. The resting nuclei, as in other
cases, show no nucleolus. Fig. 222, F to J, shows the
earliest stage in the differentiation of the spermatozoid, and this
corresponds exactly with what I have observed in various
Ferns, and differs somewhat from Buchtien*s figures of corre-
sponding stages. The nucleus, which is not noticeably lateral
in position, shows a narrow cleft upon one side. Seen in
profile (Fig. 222, F, i), one side projects somewhat more than
the other, and becomes the anterior end, which later becomes
thinner than the posterior part. I was unable to see that this
forward part behaved differently with regard to the nuclear stain
employed from the hinder part, nor could I satisfy myself of
the presence of the cytoplasmic anterior prominence which
Strasburger ^ figures in the Ferns. Staining with the mixture
of fuchsin and iodine-green, recommended by Strasburger, gave
indifferent results, both in the younger stages and the free
spermatozoids. In microtome sections, where the spermatozoids
were very strongly stained and the cytoplasm almost colourless,
the nuclear structure was unmistakable nearly to the extremity.
It is not impossible that the extreme forward end may be
cytoplasmic ; but if so, it forms but a very insignificant part of
the fully-developed spermatozoid. The cilia (Fig. 222, C) are
evident long before the spermatozoid has attained its full length,
and are shorter at first than later on. There seems little doubt
that they are direct outgrowths of the forward end, and lie close
to the convex surface of the body, so that they are easily
overlooked.

The body rapidly elongates and becomes quite homo-
geneous, but this does not occur until a comparatively late
stage. The nucleus is here somewhat flattened to begin with,
and the coils of the spermatozoid lie nearly in the same plane
and resemble a good deal those of Marattia, except that they
are larger. The protoplasm enclosed within the coils is con-

* Strasburger (ii), vol. iv. PI. III. Figs. 26, 27.

xiii EQUISETINE^ 429

spicuously granular, and forms the large vesicle attached to the
posterior coils^ of the free spermatozoid. The mucilaginous
change in the walls of the sperm cells begins about the same
time as the differentiation of the spermatozoids.

The free spermatozoids consist of from two to three complete
coils, of which the forward one or two are very much smaller
than the very large and broad hinder one, which encloses the
vesicle. The cilia are much like those of the Fern spermatozoid,
but somewhat shorter. The cover cells of the ripe antheridium
are forced apart by the swelling of the mucilage from the dis-
organised walls of the sperm cells, which are forced out of the
opening into the water, where the remaining wall of the sperm
cell is dissolved and the spermatozoid set free. When in
motion a peculiar undulation of the large posterior coil is
conspicuous, a phenomenon which has also been observed in the
quite similar spermatozoids of Osmunda.

The Archegonium

The young female prothallium is always a cylindrical mass
of cells with a series of thin lateral lobes. After the archegonia
begin to form and a definite apical meristem is established, the
formation of these lobes is almost exactly like the similar ones
in young plants of Anthoceros fusifomtis. The exact relation
of the growing point in the older prothallium to the primary
one could not be made out. In the former this arises, according
to Buchtien,^ upon the under side of the prothallium, without
any apparent relation to the primary growing point. This
much is certain, that just before the first archegonium appears,
there is formed a cushion not unlike that of the Ferns. In the
youngest condition this in profile (Fig. 223, A) shows an
evident apical cell (probably one of several), not unlike that of
the Ferns ; but the great difficulty of obtaining accurate sections
through it made it impossible to follow exactly its further
development. This much can be stated confidently, however,
that at the time when the first archegonia are produced, the
structure of the prothallium is essentially that of Osmunda or
Marattia^ and consists of a central massive midrib and a one-
celled lamina, which is not continuous, but composed of
separate lobes. A similar condition exists in Osmunda^ where

^ Buchtien (i).

430

MOSSES AND FERNS

CHAP.

in the older prothallia similar but much shorter and broader
lobes arise alternately from either side of the growing apex.

The development of the archegonium is intimately asso-
ciated with the formation of the lobes. The archegonium
mother cell is formed close to the base of the young lobe upon
the ventral side. By subsequent growth of the tissue between
it and the apical meristem, it is subsequently forced to the
upper side, but its origin is ventral, as in the Ferns. The
lobe at whose base it is borne grows for some time by a

Fig. 233.— Development of the archegonium. A, Optical section of the very young archegonial
meristem, X 235 ; B-E, longitudinal sections of young archegonia, x 450 ; c, neck canal cell ; v,
ventral canal cell ; <7, egg.

definite apical cell, which is very evident in horizontal sections
(Fig. 224, C).

The development of the archegonium most nearly resembles
that of the eusporangiate Ferns. Usually, but not always, no
basal cell is formed, and the first division in the inner cell
separates the neck canal cell from the central cell. Both neck
and ventral canal cells (Fig. 223, E) equal in breadth the
central cell, and in this respect are most like the Marattiacex.
The neck canal cell later grows up between the neck cells, but
there is usually a space between its summit and the terminal
neck cells, which here are much longer than the others. It

XIII

EQUISETINEjE

431

subsequently divides by a transverse wall, as may happen in
the Marattiaceae and occasionally in Osmunda, but whether
this always takes place is not certain (Fig. 224, A). The four
rows of neck cells are all alike, and consist ordinarily of three
cells each, the terminal ones being very long, and when the
archegonium opens bending back strongly, but not becoming
detached. The central cell is surrounded by a single layer of

Fig. 224. — A, Longitudinal section of nearly ripe archegonium, with two neck canal cells (c, c\^% 550 :
B, section of an open archegonium, x 275 ; C, D, two cross-sections of a young archegonium ; L,
the lobe at the base of which the archegonium is formed, X 550.

tabular cells cut off from the adjacent prothallium tissue, but
these divisions may extend to the lower neck cells (Fig. 224,
A). The egg is globular and shows no peculiarities of structure.
Buchtien's ^ account of the further development of the meristem,
as well as his figures,^ point to something very much like a
repeated dichotomy of the growing point ; a further investigation

^ Buchtien (i), p. 24.

432 MOSSES AND FERNS chap.

of the exact origin of the primary meristem and its relation to
the secondary ones found in the branches is much to be
desired.

Each archegonium stands between two lobes, the one from
whose base it has itself developed, and the next younger one.
As these lobes in vigorous prothallia grow to a lai^e size, and
branch, this gives the prothallium an extremely irregular out-
line, recalling very much that of Anthoceros punctatus or A.
fusiformis. These branching lobes are not to be confounded
with the branches of the prothallium body due to the dichotomy
of the archegonial meristem. These latter are always short,
and project but little compared to the secondary branching
lobes produced from them. The entrance of the spermatozoids
and the changes subsequent to fertilisation seem to be exactly
the same as in Ferns.

The prothallia are normally dioecious, but this is not
exclusively the case. To a certain extent the external con-
ditions influence the production of males or females, as in the
Ferns, and unfavourable conditions of nutrition tend to increase
the proportion of the former.

According to Hofmeister ^ the number of archegonia upon
vigorous prothallia varies from twenty to thirty. His statement
that this exceeds the number of antheridia in the larger male
prothallia is not confirmed by Buchtien,^ who found as many
as 1 20 of the latter in some cases.

Usually more than one archegonium is fertilised, Hofmeister
having found as many as seven embryos upon a single pro-
thallium. He does not state how many of these develop.
The embryo corresponds closely to that of the Ferns, and has
been carefully described by Sadebeck.^

The Embryo

The fertilised egg grows until it completely fills the ventral
cavity, and its granular contents become more separated, and
the nucleus is decidedly larger than before fertilisation. The
lower neck cells approach and apparently become grown
together, and as the divisions in the lower neck cells here
contribute to the calyptra, the young' embryo becomes more

' Hofmeister (i), p. 301. • Buchtien (i), p. 22.

' Sadebeck; Pringsheim's **Jahrb. fiir wiss. Botanik," 1878.

XIII

EQUISETINE^

433

deeply sunken in the prothallial tissue than is common in the
Ferns. The basal wall is transverse, as in the Marattiaceae, and
the formation of the quadrants takes place as usual. The
position of the quadrant walls is, however, sometimes slightly
different, being often decidedly inclined in both epibasal and
hypobasal halves (Fig. 225, E). In the former the larger of
the two primary cells is the initial for the stem, and its large
size, compared to the leaf quadrant, already points to the
greater development of the stem in the sporophyte compared

Fig. 235. — A, Longitudinal section of the venter of a recently fertilised archegonium, X300; B, a
similar section of an archegonium with the young embryo ; C, D, two transverse sections of a
somewhat older embryo, X 300 ; */, apical cell of the stem ; r, apical cell of the root ; E,
longitudinal section of an older embryo, X300; I, I, the basal wall.

to the leaves. Of the hypobasal quadrants the larger becomes
at once the root, whose axis is coincident with that of the stem.
The first two divisions in the stem quadrafit establish the
definitive apical cell, which occupies nearly the centre of the
epibasal part of the embryo, and is surrounded by a circle of
four cells, two of which belong to the leaf quadrant (Fig. 225,
C), and two are segments of the stem quadrant, the first one
corresponding morphologically to the second leaf of the Fern
embryo. This circle of cells forms the first sheath about the

2 F

434 MOSSES AND FERNS chap.

stem of the young sporophyte. After one set of lateral
segments has been cut off from the root quadrant, the primary
cap cell is formed as in the Ferns. Unlike the latter, the
divisions in the stem apex proceed rapidly, and it soon projects
in the centre of the embryo as a broad conical prominence,
terminating in the large tetrahedral apical cell.

The three parts of which the primary leaf- sheath is com-
posed remain distinct and form the three teeth (Fig. 226, C),
which grow rapidly until they are about on a level with the
apex of the stem. This growth is mainly due to the activit>'
of the marginal cells. The root grows less actively at first
than either stem or leaves, and at the time the latter is nearly
fully developed forms but a small prqtuberance at the base of
the embryo (Fig. 226, C). The foot at this time is not
conspicuous, but later enlarges more. Its cells are in close
contact with the prothallial cells. The root now grows rapidly
downward, penetrating through the prothalHum until it reaches
the ground. The stem apex next rapidly elongates and grows
upward through the calyptra. The embryo thus perforates the
prothallium both above and below, as in Marattia, although
owing to the position of the archegonium in the former the
relation of the embryo to the latter is not the same.

Hofmeister states ^ that the vascular bundles are not formed
until after the primary organs have broken through the pro-
thallium, but this point needs further examination.

The development of the primary axis, unlike that of the
Filicineae, is limited, and it ceases growing after producing
ten to fifteen sheaths, which, like the first one, are three-toothed.*
The stem remains very slender, but shows the marked division
into nodes and internodes found in the later ones. This
primary stem has irregular lacunae in the cortex, but does not
show the cavity so conspicuous in the central part of the older
plant, and in E, telmateia^ according to Buchtien,^ this is quite
solid. In this species he figures four vascular bundles, whose
xylem is relatively much better developed than in the later
stems. The bundles, like all of those in the stem and leaves,
are collateral, and the whole group is surrounded by a well-
marked endodermis. From the base of this primary shoot a

^ Hofmeister (i), p. 303.
^ Buchtien states that in E, variegatttm they are only iwo-toothcd
i, ^ Buchtien (i), Fig. 119.

XIII EQUISETINE^ 435

second stronger one grows. Hofmeister^ states that the bud
is an adventitious one, arising endogenously, but it is much
more likely that it is an axillary one, like all the later buds,
and formed in the axis of the cotyledon. This point does not
appear to have been examined by either Sadebeck or Buchtien.
This second shoot is much more vigorous, and its leaf-sheaths
have four teeth. From the base of this others arise in the
same way and in rapid succession. Sometimes the third, or
one or more of the later formed basal shoots, bends downward
and penetrates the earth, producing the first of the character-
istic rhizomes. The first of these have also four-toothed sheaths,
but the branches produced from them gradually assume the
characters of the fully -developed shoots, some of which
ultimately bear sporangia. The first shoots of the sporophyte,
even in such species as later branch very freely, produce only
an occasional branch, which breaks through the base of the
sheath. Whether in these early stems a bud is formed nor-
mally at the base of each tooth does not .appear to have been
investigated. Numerous roots are found at the nodes of these
rhizomes, which probably originate, as in the aerial stems, from
the bases of the buds in the axil of the sheath.

The Mature Sporophyte

On comparing the sporophyte of Equisetum with that of
most Ferns, the greatest contrast is in the relative importance
of stem and leaves. The stem in all the Equisetineae is extra-
ordinarily developed, while the leaves are rudimentary, in strong
contrast to their great size and complexity in many Ferns.
All species of Equisetum produce a more or less developed
underground rhizome, which often grows to a great length and
ramifies extensively. This, like the aerial branches developed
from it, shows a regular series of nodes and internodes. The
latter are marked by longitudinal furrows, and about each node
is a sheath whose summit is continued into a number of teeth,
varying with the size of the stem. Corresponding to each
tooth of the sheath there is developed an axillary bud, which
may either at once develop into a shoot, subterranean or
aerial, or these buds may remain dormant for an indefinite
period, being capable of growing, however, under favourable

' Hofmeister (I), p. 303.

436

MOSSES AND FERNS

CHAP. XIII

conditions. The surface of the rhizome in E. ielmateta^
especially at the nodes, is covered with a dense dark -brown
felt of matted hairs, and a whorl of roots occurs at each node,
corresponding in number to the number of axillary buds, from
whose bases the roots really grow. Sometimes the buds
become changed into tubers (Fig. 227), which are especially
common in E, telmateia and E. arvense. These tubes are
protected by a hard brown sclerenchymatous rind, within
which is a mass of starchy parenchyma, traversed by the slender

Fig. 226. — A, An advanced embryo of E. arvenst (L.X surface view, X360; B» optical section of a
similar stage of E. palusire (L.), X 360 ; C, older embryo of E. arvense (L.), X 160 ; st^ stem ; R,
root (all the figures after SadebeckX

vascular bundles. In some cases these buds form in chains
and are then seen to be the swollen intemodes of short
branches.

The aerial stems are of two kinds, sporiferous and sterile.
In one group the only difference between the two is that the
former bear at the apex the sporangial strobilus ; in the second,
of which E. telmateia is an example, the sporiferous branches
are almost entirely destitute of chlorophyll and quite unbranched,
whilp the green sterile shoots are extensively branched. In
such forms the fertile shoots die as soon as the spores are shed,
and usually appear before the green shoots are developed.

Fig. 2a7.— a, Upper part of a fertile shoot of E. telmatcia^ x i ; B, lower part of a vegetative shoot,
with young branches for the next season's growth, X i ; T, tubers ; C, cross-section of an inter-
node of the fertile shoot, X4; L, cortical lacunae ; D, sporangiophores, X4; £, median section
of a single sporangiophore, x 6 ; x/, sporangia.

438

MOSSES AND FERNS

Tfte Stem ^

A longitudinal section of one of the numerous subterranean
buds (Fig. 228) shows that the conical apex of the stem is
^occupied by a large pyramidal cell whose segmentation is
exceedingly regular. The youngest of the foliar sheaths is
separated from the apex by several segments, but below, the
next older sheath is very close to it, and the intemode, which
in the older stem is so conspicuous, is scarcely perceptible.
The closely-set sheaths grow very rapidly, so that all but the
youngest ones extend beyond the stem apex, which is thus

Fig. 228. — A, Median section of a strong subterranean (vegetative) bud, x 30 ; *, lateral bod •
B, the apex of the same section, X 200.

very completely protected. They form a compact, many-
layered covering about it, presenting very much the appearance
of the leaf-buds of many Spermaphytes. The apical cell shows
the usual three series of lateral segments. These are arranged in
three rows, but owing to a slight displacement in the younger
ones, the teeth of the sheaths alternate. Each cycle of three
segments comes to lie practically in the same plane, and con-
stitutes a disc which later forms a node and intemode of the
stem. Each segment is first divided by a wall nearly parallel
to the wall by which it was cut off from the apical cell, into
two overlying cells. The upper cells or semi-segments give
rise to the nodes, the lower to the internodes.

* Rees (2) ; Sachs, see Goebel (10), p. 261 ; Janczewski (3).

xiii EQUISETINE^ 439

The next walls are like the sextant walls in the roots of
the Ferns, and a cross-section just below the apex presents
exactly the same appearance. Each cell now divides by walls,
apparently not always in the same order, parallel with the
primary and lateral walls, and very soon there are periclinal
divisions by which an inner cell is cut off from each segment
cell that extends to the centre. This primary group of central
cells is the pith, which later in the internodes is usually torn
apart and destroyed, leaving the large central hollow met with
in all the larger species of Equisetum. From the outer cells
are developed the leaves, the vascular bundles, and cortex.

The annular leaf-sheaths begin as outgrowths of the super-
ficial nodal cells of each cycle of segments, and these form a
circular ridge or cushion running round the base of the apical
cone. The summit of this ridge is occupied by a row of marginal
cells, which are the initial cells, and from which segments are cut
off alternately upon the inner and outer sides (Fig. 233, A).
The growth is stronger at certain points, which, according to
Rees,^ have a definite relation to the early divisions. Thus in
E. scirpoides the teeth are always three, and correspond to the
primary nodal cells ; in E, arvense there are six or seven, in
the first case corresponding to the sextant cells, in the latter to
the sextant cells plus the first division in one of them. In the
large species, like E. telmateia^ it is difficult to trace any such
relation. In most forms, by subsequent dichotomy of some or
all of the primary teeth, others are formed, so that the number
in the fully-developed sheath exceeds that first formed. As
soon as the young sheath begins to project, a section through
one of the teeth shows that it is divided into an upper and
lower tier of cells, the apical cell terminating the upper one.
This division no doubt corresponds to the first horizontal
division in the outer nodal cell from which the leaf-tooth
originally comes. In one a little older (Fig. 233, B), in this
upper tier of cells a line of cells occupying the axis is evident
{fb\ extending from the base of the leaf nearly to the summit,
and growing at its outer end by the addition of cells derived
from the inner part of the youngest upper segments of the
terminal cell of the leaf.^ This is the beginning of the single
vascular bundle found in each leaf.

* Rees (2), p. 228.
' Each tooth is here regarded as a leaf, the sheath as a circle of confluent leaves.

440

MOSSES AND FERNS

CHAP.

Shortly after this first indication of the vascular bundle of the
leaf can be seen, the cells of the cortex immediately outside the
central pith begin to divide rapidly by longitudinal walls and form

Fig. 339.— Transverse section of a young vegetative shoot just below the apex, X260; B, outer part
of a section lower down, X 260 ; /r, procambial zone ; C, young vascular bundle, x 530 : /.
primary tracheids.

a zone of cambiform cells completely surrounding the medulla-
In the primary central row of cells in the leaves similar 'divisions
occur, and a very evident procambium cylinder is formed, bending

XIII

EQUISETINE^

441

in and joining the procambium zone of the cortex. At the point
of junction the cells are shorter and broader, and the cortical
cells lying outside are also much broader, so that the cortical
procambium is very conspicuous. If cross-sections are ex-
amined about this time, in the procambium zone are found a
number of groups of cells where the divisions are more rapid,
and the resulting cells narrower than the surrounding ones.
These are the separate vascular bundles, and are continuous
with those in the leaves (Fig. 230). The first permanent
tissue consists of one or two small annular tracheids upon the

Fig. 330. — Longitudinal section of the young stem, showing the junction of the foliar and internodal
bundles ; /r, the primary tracheids ; x, x, tannin-bearing cells.

inner side of the bundle (Fig. 229, C). These are followed by
several others. They first form in the internodal part of the
bundle and only later in the foliar portion. The nodal
tracheids joining the xylem of the foliar and internodal bundles
are very irregular short cells with annular thickenings upon
their walls. Later two small groups of larger spiral tracheae
are formed at the sides of the xylem, but the greater part
remains but little changed. By this time, in E. telmateia,
numbers of cells with peculiar contents are noticed scattered
through the pith and cortex (Fig. 230). The contents of

442 MOSSES AND FERNS chap.

these are dense, and stain deeply, indicating the presence of
mucilaginous matter, and probably tannin, their appearance and
behaviour being very much like the tannin cells of Angiopteris
or Maratita.

In the older parts of the section the nodal cells remain
short, while the internodal cells elongate very much and sepa-
rate the nodes with their attached foliar sheaths. With this
growth is associated the formation of the characteristic lacunae.
In all the large species the growth of the medullary cells very
soon ceases to keep up with the expansion of the stem, and
they are torn apart and almost completely disappear, leaving a
great central cavity in each internode separated from the
neighbouring ones by a thin diaphragm, — all that is left of the
medulla in the fully-developed stem. The leaves of successive
sheaths alternate, and a study of the course of the vascular
bundles shows that at each node the alternating bundles of
successive intemodes are connected by short branches. Corre-
sponding to the vascular bundles are ridges upon the surface of
the internodes and foliar sheaths, due to greater growth at these
points, as a result of which a regular series of cortical lacunx
(vallecular canals) is formed, alternating with them (Fig. 227, C),
and lying just outside of the cortical zone containing the
vascular bundles. In some of the small species of Equisetum,
as in the primary shoot, the central lacuna is absent.

A cross-section of the fully-developed stem of E. teltnateia
(Fig. 227, C) shows this very regular arrangement of the
vascular bundles and lacunae. In addition to the large cortical
ones, each vascular bundle has, on the inner side, a lai^e air-
space, which like the other is formed by the tearing apaut of
the tissues of the bundle. In this way the primary tracheids
are torn apart and often destroyed, so that all that remains of
them are the isolated thickened rings adhering to the sides of
the canal. The bundle is strictly collateral in structure, and
very much resembles that of many grasses and other simple
Monocotyledons. The phloem is composed of sieve -tubes,
which, according to Russow,^ have only horizontal sieve-plates,
and no lateral ones as in the Ferns. These are mingled with
cambiform cells. In the species in question there is in addition
a zone of bast fibres, at the outer limit of the phloem.

Surrounding the whole circle of bundles in E, teltnateia,

* Russow (i).

xin EQUISETINE.^ 443

E, arvensey and several other species, there is a common endo-
dermis (Fig. 231, en). In others the arrangement is different.^
Thus in E, limosuniy each separate bundle has its own endo-
dermis ; in E. hiemale there is a common inner as well as an
outer endodermis in the aerial stems, while the bundles of the
rhizome are like those of E. limosum. Inside the endodermis lies
the single pericycle.

All the cortical cells are separated by small intercellular
spaces, which are very conspicuous in the soft tissue of the
fertile stems of E, telmateia and E, arvense. In all of the

Fig. 231.— Transverse section of the vascular bundle of a fully-developed vegetative shoot, X75 ; /, f,
lacunae ; x^ x^ tannin cells ; /, /, remains of the primary tracheids ; r«, endodermis.

internodes of the main axes of E, telmateia chlorophyll is
absent, but in most species the principal assimilative tissue is
situated here. It consists usually of isolated masses of trans-
versely extended green cells separated by strands of colourless
sclerenchymatous fibres, which form the ridges so prominent
upon the internodes and foliar sheaths. Seen in cross-section
the masses of green cells are concave outwardly and lie
beneath the grooves between the ridges. In secondary branches

* PfiUer (I), p. 292 ; Van Tieghem (6), p. 365.

444 MQSSES AND FERNS chap, xiii

the amount of this tissue is much greater and the lacunae less
conspicuous, or indeed even wanting.

The epidermis, as is well known, contains great quantities
of silex, which gives it its very rough and harsh surface. This
is deposited either uniformly, as is usually the case- in the
lateral cell walls, or in tubercular masses. Upon the inner
surface of the guard cells of the stomata it forms regular
transverse bars (Fig. 232). Upon the outer walls of the
epidermal cells the masses form either isolated bead -like
projections or these are more or less completely confluent.

The stomata are peculiar in structure, and their development
was first correctly described by Strasburger.^ In E, tehnateia
these only occur usually upon the foliar sheaths, but in species
with green internodes they are found principally upon the sides
of the furrows over the green hypodermal tissue.^ Before the
stoma proper is formed, the cell divides twice by longitudinal
walls (Fig. 232), and the original cell is thus divided into a
central one (the real stoma mother cell) and two narrow lateral
accessory cells. The central cell now divides again, and the
division wall splits in the centre as usual. A cross-section of
the young stoma (Fig. 232, D) shows that the walls by which
the accessory cells are cut off are inclined, so that the stoma
cell is broader at the bottom than at the top, and as develop-
ment proceeds the accessory cells completely overarch the
stoma, and in the older ones look as if they had arisen by
horizontal divisions in the primary guard cells. The accessory
cells show the same tuberculate silicious nodules upon their
outer walls as the other epidermal cells, and upon the inner
face of the real guard cells only are formed the regular bars.
Stomata are quite absent from the rhizome, and also from the
colourless fertile branches of E, telmateia. Compared with the
aerial stems, the rhizome shows a smaller number of vascular
bundles, and a corresponding reduction in the number of the
lacunae.

Until the researches of Janczewski ^ and Famintzin * it
was supposed that the lateral branches arose endogenously.
Their researches, however, showed conclusively that this was

^ Strasburger (i).

* Miss E. A. Southworth (i) found that in E, arvense they occur upon the ridges,
and upon the fertile as well as the sterile shoots.

' Jancrewski (3). * Famintzin (l).

(^.

fi X

5,^

i-'

Fig. 232. — Development of the stomata. A-C, Surface views of very young stomata of £, Uimateiay
X 600 ; D, section of an older stoma of E. limosum^ x 700 (after Strasburger) ; E, outer surface of
a complete stoma of E. telmateia^ showing the silicious nodules upon the epidermal cells ; F,
inner side of the same, showing the silicious bars upon the inner walls of the guard cells ; r, 7%
accessory cells ; j, guard cells.

446

MOSSES AND FERNS

not the case, but that the origin was exogenous. In most
species these are produced abundantly, and a bud is formed in
the axil of each leaf, although it frequently happens that some
of them do not develop fully. In E. tehnateia they do not
form at all, as a rule, upon the colourless sporiferous shoots,
but are regularly formed from all but the lowest nodes of the
sterile stems. In E, sdrpoides they are absent from all the
aerial stems, but whether rudiments of them are formed does
not seem to have been investigated.

Their development may be readily traced in a series of

Fig. 333. — Longitudinal section of a young vegetative shoot, showing two young leaves (L.X xaoo;
B, section passing through the base of a somewhat older leaf ;y^, vascular bundle; C, section
passing through a young bud {fi).

median longitudinal sections through a vigorous sterile stem of
E, telmateia or E, arvense before it appears above ground.
The young bud (Fig. 233, C) originates from a single epidermal
cell just above the insertion of the leaf. This cell enlarges
and is easily recognisable. In it are formed three intersecting
walls cutting out the apical cell, which at first is somewhat
irregular, but soon assumes its definite form, and the subsequent
growth of the branch resembles in all essential points that of
the main shoot. Very early the cells of the leaf-base immedi-
ately above the young bud grow around it like a sheath, and

EQUISETINEjE

447

finally become grown together with the epidermal cells of the
axis above the bud, which thus lies in a completely closed cavity.
As the bud grows it gradually destroys the tissue surrounding
the cavity, and finally breaks through the base of the leaf,
appearing from the outside as if it had developed from below
and not from the axil of the leaf. In most species these

Fig. 234.— Section of a lateral bud, enclosed within the sheath fonned by the leaf-base, x 175.

branches remain simple, but in E, sylvaticum and E, gtganteum
the secondary branches also ramify.

Tlie Roots

The formation of the roots is intimately connected with
that of the lateral buds. Each bud normally produces a single
root below the first foliar sheath, which in the buds derived from
the rhizome all develop, whether the buds themselves grow
further or not According to Janczewski, certain of these
rhizogenic buds of the rhizome produce several roots, but the

448

MOSSES AND FERNS

CHAP.

buds remain otherwise undeveloped. In the aerial stems the
roots remain normally undeveloped, but may often be stimulated
into growth by keeping the stem moist and dark.

Van Tieghem ^ describes the roots of E. palustre as being
exogenous, and says they can be traced to a definite cell of one
of the young segments. Janczewski,^ however, was unable to
recognise the young root until the first foliar sheath was well
developed, and in E. telmateia I could see no trace of the
root in still older buds, and they were apparently always of

Fig. 235.— a, Longitudinal section of the root apex, x aoo ; jr, x, the large central \'essels of the
vascular bundle ; B, C, two transverse sections passing through the apex, X200. In C b shown
the first divisions of the cap cell.

endogenous origin, although this point was not closely in-
vestigated.

The structure of the apical meristem is much like that of
the leptosporangiate Ferns, the main difference being the greater
development of the root-cap, in which periclinal walls are
frequent, so that the older layers, especially in the middle, are
several cells thick, and not clearly limited.

After the sextant walls are formed, each semi-segment is
divided at once into an inner and an outer cell, the former

* Van Tieghem (5), p. 551.

- Janczewski (3). p. 89.

EQUISETINE^

449

giving rise directly to the plerome. The next division (seen in
longitudinal section) separates the epidermis initials from the
cortex. A cross-section of the young plerome immediately
after the first divisions have taken place (Fig. 236, A) shows
that the three primary cells are of unequal size, and that the
two smaller ones divide first. From the larger one, the first
periclinal wall separates a central cell, which occupies almost
exactly the middle of the section, and this stands immediately
above the corresponding one in the older segments, so
that in longitudinal sections these form a very conspicuous
axial row of cells {x, x\ which together constitute the single
large vessel which occupies the centre of the older bundle.

Fig. 236.-— Three transverse sections of the young root, x 200 ; en, endodermis ; v, central vessel.

The endodermis becomes separated by this time, and a little
lower down divides by periclinal walls into the two layers found
in the completely developed root. The tissues of the central
part of the young root are very regularly disposed (Fig. 236,
B, C). In the centre is the large vessel already described,
around which ^re arranged at first a single row of usually six
or eight cells (Fig. 236, B). By these first divisions the separa-
tion of the xylem and phloem of the bundle is complete. If
there are six of these primary cells the bundle will be triarch,
if eight, tetrarch. In somewhat older sections of a tetrarch
bundle (Fig. 236, C) four of the primary cells are still recognis-
able and have divided but little. These form the four groups

2 G

450 MOSSES AND FERNS chap.

of tracheids of the older bundle. The intermediate cells divide
much more rapidly and constitute the phloem. The number
of endodermal cells in a cross-section corresponds generally to
the number of xylem and phloem masses. The peripheral
groups of tracheae early develop spiral thickenings upon their
walls, and sometimes there is but a single row of tracheae in each
xylem mass. Each of the three phloem masses of E. variegatum
has tliree narrow sieve-tubes in contact with the inner endodermis
surrounded by thin-walled cambiform cells. The thickenings
upon the walls of the large central vessel form only at a late
period.

Intercellular spaces arise at the angles of the outer endo-
dermal cell, and similar ones also between the outer cells of
the cortex, which becomes very spongy in the older roots.
Numerous brown root-hairs, like those upon the rhizome, cover
the surface of the root. A pericycle is quite absent, and the
secondary roots arise from the inner endodermis in direct con-
tact with the tracheids. The latter, as will be seen from the
figure, lie between two endodermal cells, and the young root
lies therefore not directly opposite, but to one side of the
corresponding xylem mass. The young roots may arise from
either of these endodermal cells, and consequently there is
formed a double row of rootlets corresponding to each xylem
mass of the bundle. Shortly after the rootlet is formed, the
endodermal cell outside it divides by a tangential wall, and
this develops into a double layer of cells completely enclosing
the young rootlet.^ A similar "digestive pouch" is formed,
according to Van Tieghem, in the roots of many Ferns, but is
in these derived from the cortex outside the endodermis. The
double endodermis of the bundle of the older root shows the char-
acteristic foldings of the radial walls only upon the outer cells.

Cormack ^ has recently published a paper showing that in
E, maximum {telmateia) there is a slight secondary increase in
thickness in the nodes of the stem, due to the presence of a
genuine cambium, not unlike that in the stem of Botrychium.

The Sporangia

In all species of Equisetum the sporangia are formed upon
the under side of peltate sporophylls arranged in closely -set

» Van Tieghem (5), p. 395- ^ Cormack (i).

EQUISETINE^

451

circles about the upper part of the axis of the fertile shoots
(Figs. 227, 242). A section through the apex of the young
shoot shows much the same structure as a sterile one, but
the apical cell is smaller and the leaves do not arise so
near the summit. Circular foliar sheaths are formed in the
same way, but the leaves form rounded elevations, either
entirely separated or but slightly joined (Fig. 237). These
are at first nearly hemispherical, but soon become constricted
at the base, and about the same time the first trace of the
sporangia can be seen. A section of the young sporophyll

Fig. 337. — A, Longitudinal section of the apex of a young fertile shoot, x i6 ; B, apex of the same,
X 160 ; x/, young sporangiophore ; jr, apical cell.

shows that the centre of the prominence already has formed
the young plerome which, as in the ordinary leaves, joins that
of the internode beneath. Just above the base a cell may
sometimes be detected, which is larger than its fellows, and
has a larger nucleus. From a comparison with slightly older
stages there is no doubt that this is the sporangium mother
cell, or more correctly the axial sporangial cell, as the adjacent
tissue also takes part in its further growth. This axial cell
now becomes separated into an inner and outer cell, as in
Botrychium, The outer cell divides again. The innermost

452

MOSSES AND FERNS

cell of the axial row is the archesporium, and gives rise to the
sporogenous cells by repeated divisions, at first at right angles
to each other, later in all directions. Bower ^ thinks that all
the sporogenous cells are not to be traced back to the single
archesporial cell, but that the inner of the two cover cells also
takes part in spore-formation. The exact limits of the arche-
sporium are difficult to follow, as the contents of the sporo-
genous cells are not strikingly different from the inner tapetal
ones. These are derived from the cells adjacent to the axial

Fig. 238. — A, Longitudinal section of young sporangiophore, shovving the primary sporangial cell (i;^X
X 260 ; B, C, longitudinal sections of young sporangia, x 260. The archesporial cells are shaded.

row, and from the cells of the latter just outside the archesporium.
The wall of the sporangium is mainly formed from the cells
adjacent to the axial row of cells. All the cells grow and
divide rapidly, so that the sporangium soon projects strongly
from the margin of the sporophyll, whose upper part becomes
broad and flattened, while the stalk increases but little in
diameter. The wall of the sporangium at first is three or four
cells thick. Finally it is reduced to but a single complete

1 Bower (15), p. 497.

XIII

EQUISETINE^

453

layer by the absorption of the others, but the remains of a
second layer can be made out in stained sections of the ripe
sporangium (Fig. 241, E). The vascular bundles of the sporo-
phyll branch, one branch running to each sporangium.

Of the two species studied by Bower, E, arvense and E,
limosum, the latter showed more slender and strongly projecting
sporangia, but otherwise they were alike. E. telntateia has
even more massive sporangia than E, arvense. The sporo-
phylls form a regular cone at the apex of the fertile branch,
and are arranged in regular whorls, which vary in number in

Fig. 239. — Longitudinal section of an older sporangium, x 260. The nuclei are shown in the arche-

sporial cells.

proportion to the size of the cone. The top of the sporophyll
is always polygonal in outline, owing to the lateral pressure of
its neighbours, and very often they are regularly hexagonal,
but this bears no relation to the number of sporangia, which
usually exceed in number the angles of the sporophyll.

Development of the Spores

The development of the spores in Equisetum^ while agree-
ing in many respects with that of the eusporangiate Ferns,
shows some peculiarities that are noteworthy, and as this offers
one of the best cases for studying spore -formation, it was

454 MOSSES AND FERNS chap.

somewhat carefully followed in E. telmateia. After the com-
plete number of cells has been formed in the archesporium, and
before the tapetal cells are broken down, the sporogenous cells
are divided into groups which begin to separate from each
other. With the enlargement of the sporangium and the
breaking down of the inner tapetal cells these masses become
isolated, and are very easily removed from the sporangium (Fig.
240, A). They usually consist of four cells, which in water
swell up somewhat. In a fresh condition they appear quite
colourless, but the cytoplasm is densely granular. The nucleus
is very large and appears quite transparent with one or two
distinct nucleoli. In material treated with osmic acid, what
appeared to be the centrospheres were seen, but not very
clearly. In microtome sections of about the same age (Fvg.
240, B) the numerous rod-shaped chromosomes were very evident,
but their number could not be determined. The nucleolus is
conspicuous, and on one side, in a slight depression in the
nuclear membrane, are the two centrospheres. These latter
were not always perfectly evident, but are probably always
present. The radiating lines about them were not seen.
Before the final division takes place, the sporogenous cells
become completely rounded off, and are embedded in a mass
of nucleated protoplasm (Fig. 241, A) derived from the tapetal
cells, but also in part from some of the archesporial cells which
do not develop into spores.^

Fig. 240 shows the successive stages in the process.
During the division of the primary nucleus there is an evident
cell plate forn\ed (Fig. 240, E), but no division wall. The
period at which the centrospheres divide could not be made
out, but by the time the division is complete each nucleus is
provided with two, which are decidedly smaller than the
primary ones. During this first division there is probably a
reduction in the number of the chromosomes, as in Osmunda,
At any rate the number is evidently much smaller during the
metaphases of the second nuclear divisions (Fig. 240, F). The
second divisions are the same as the primary one, and the
planes of the two nuclear spindles may either be parallel or at
right angles (Fig. 240, F). In either case the resulting nuclei
arrange themselves at equal distances from the centre of the
cell, and the connecting filaments are formed between them.

1 Bower (15), p. 500.

XIII

EQUISETINE^

455

In the connecting spindles is formed between each pair of

cen. D.

Fig. 24c.— Development of the spores. A, Group of four sporogenous cells, x 600 ; B, section of a
single sporogenous cell, just before the first division of the nucleus, X X3oo ; D-H, successive stages
in the division of the nuclei, X 1300 ; cen^ centrospheres ; n«, nucleolus.

nuclei a cell plate, which here soon develops into a definite
cellulose membrane, and the spores separate completely.

456

MOSSES AND FERNS

The young spore has at first a very delicate cellulose
membrane, which thickens, and later has separated from the
outside the "middle layer" (Fig. 241, B, w), which in spores
placed in water lifts itself in folds from the underlying exospore.
The outer perinium seems to be unquestionably formed through
the agency of the nucleated protoplasm, in which the young
spores lie. It is at first a uniform membrane, closely applied
to the middle coat, but when placed in water it swells up and
n.

Fig. 241.— a, Group of sporogenous celk, just before the final division into the spores, embedded in
the nucleated protoplasm formed from the disintegrated tapetum, and sterile archesporial cells,
X 500 ; B, optical section of young spore, showing the three membranes ; w, the middle lamella,
X 500 ; C, an older spore, showing the splitting of the outermost coat to form the elaters, x 500 ;
D, surface view of the dorsal cells of the wall of a ripe sporangium,- X 150 ; E, section of the waH
showing the remains of the inner layers of cells {t\ X 250.

separates completely from the exospore, or remains attached to
it at one point only, which marks the point of attachment of
the elaters in the ripe spores. The elaters arise from the
epispore by its splitting spirally into four bands (Fig. 241, C),
due apparently to thickening along these bands, leaving thin
places between, which are finally absorbed. The outside of
the elaters becomes cuticularised. The ripe spores contain
numerous chloroplasts, which only are evident in the latest
stages of development. In -£. arvense the formation of the

EQUISETINE^ 457

sporangia begins nearly a year before the spores are shed, and
they are completely developed during the preceding autumn.
The growth of the fertile branch and the scattering of the
spores take place very soon after growth begins in the spring.
Whether in cold climates E, tebnateia behaves the same way
I cannot state ; but in California, where growth continues all
the winter, the development of the sporangia is gradual, and
the fertile stems grow up and scatter the spores as soon as
they are ripe. The ripe sporangia are oblong sacs, whose wall
is composed for .the most part of a single layer of elongated
cells, marked with spiral thickened bands upon the dorsal
surface and rings upon the ventral cells, where the longitudinal
slit by which the sporangium opens is placed (Fig. 241, D, E).
The internodes in the strobilus are very little developed, but as
the spores ripen there is a slight elongation, by which the
sporophylls are separated.

Classification

Milde ^ divides the genus into two, Equisetutn {Equiseta
phanopora\ in which the accessory cells of the stoma are on a
level with the surface of the epidermis ; and Htppoc/tate {E.
cryptopord)^ in which the stomata are sunk in depressions of the
epidermis. In the former group are two divisions, those which,
like E, arvense and E. telmateia, have the fertile and sterile
branches different, and those where they are alike, e,g. E. limosum
(Fig. 242, A). In the former group some species, eg, E. pratense,
have the fertile stems at first colourless, but afterwards forming
chlorophyll and developing branches. In Hippochate, which
includes among American species E, hiemale, E. robustrntty E.
variegatum and E, scirpoides (Fig. 272, B), the aerial branches
are all similar and often are quite unbranched. The foliar
sheaths show considerable variation. In the fertile stems of E,
tebnateia (Fig. 227) they are extremely large and the ribs very
prominent, but the separate leaves are not all distinct at the
apex, but the sheath splits into a few very deeply cleft pointed
lobes. In the sterile shoots, however, and in all the stems of
most species, the teeth are very distinct and the foliar sheath
much shorter. The number of teeth varies from three in

» Milde (I).

Fic. S49. — A, Equisetum limotum (L.)t x i ; B, ^. scirfcidts (Michx.), x 2.

CHAP. XIII EQUISETINE^ 459

E, sctrpoideSy to thirty to forty, or even more, in E. telmateia and
E. robustum.

Fossil Equisetinece

To this class are usually assigned two groups of fossil
plants, one belonging to the Equisetaceae, and represented by
the genus Equisetites^ which evidently was very close to the
genus Equisetum^ if not identical with it. The other group, the
Calamarieae, differed in some respects from the living forms, and
there is much diversity of opinion about their real affinities.
The best known members of this order are the Calamiteae,
whose anatomical structure is well known. Cormack^ has
recently made a comparison of the structure of these with
EquisetufHy and comes to the conclusion that the type of
structure is essentially the same. The general points of
difference are the completely separate leaves of the Calamites,
the frequent absence of diaphragms at the nodes, and the
marked secondary thickening of the vascular bundles. Cormack
has shown that a slight thickening of the same character occurs
in the nodes of E. maximum, and in the Calamiteae this thicken-
ing seems to begin in the nodes and to extend later to the inter-
nodes. Cormack concludes that all the Calamiteae possessed
this secondary thickening of the stem. The two groups
Annularieae and Asterophylliteae, which have slender stems with
regular whorls of leaves at the nodes, have been found to be
to some extent, at least the smaller branches, of indubitable
Calamiteae ; but it is questionable whether this is always so.^

The most important remains of this group are the fossils
known under the name Calamostachys. These are cone-shaped
structures, whose close affinity with Equisetum is beyond
question. The whorls of sporophylls, which are peltate, like
those of Equisetum^ and bear four sporangia upon the lower
surfaces, are separated by alternating whorls of sterile leaves.
Through the kindness of Dr. D. H. Scott* I have had an
opportunity of examining a beautiful series of sections of C.
Bitmeyana. The structure of the axis and sporangia corre-
spond in the closest manner to those of Equisetum, but a
most interesting difference is the fact that this genus was
heterosporous. Macrosporangia and microsporangia occurred
in the same strobilus, but the difference in the size of the
^ Cormack (i). ' Solms-Laubach (2), p. 323. » Scott and WUliamson (i).

46o MOSSES AND FERNS chap, xiii

spores is much less than in the living heterosporous Filicineae
or Lycopodineae.

The Calanmarieae are all very ancient types. The first
certain remains of them occur in the Upper Devonian, and they
disappear before the Trias.^

Affinities of the Equisetinece

The Equisetineae, as will be seen from the account of the
fossil forms, are a very ancient group, and their relation to the
other Pteridophytes somewhat problematical. The modem
forms being so restricted in number and type, offer but partial
means of comparison ; still a comparison of these with the
simpler Filicineae does indicate some affinity between the two
groups, although, as might be expected, a very remote one.
Van Tieghem ^ has shown that the structure and arrangement
of the vascular bundles in the stem of Ophioglossum and
Equisetum have much in common, and a careful study of the
development of the bundles in the young sporophyte of the
latter may perhaps show still further resemblances. As we have
seen, the prothallium is not essentially different in Equisetum
and the eusporangiate Ferns, and the spermatozoids are closely
like those of the latter, and not at all like those of the Lyco-
podineae. This latter point I believe to be one of g^reat
importance.

If the Equisetineae do come from a common stock with the
Ferns, they must have branched off at a very remote period,
long before the latter had become completely differentiated.
The very different importance relatively of the stem and leaves
in the two groups points to this, as well as the extremely
dissimilar character of the sporophylls. The genus Equisetum
is evidently but a reduced remnant of a once predominant
type of plants which has been crowded out by the more
specialised Ferns and Spermaphytes. The presence of hetero-
spory is interesting, but from what we know at present it
never developed to the same extent as in the other groups of
Pteridophytes.

^ Solms-Laubach (2), p. 322. ^ Van Tieghem (6).

CHAPTER XIV

LYCOPODINE^

The Lycopodineae, though far exceeding in number the species
of Equisetunty are inferior in number to the Ferns. Baker ^
enumerates 432 species, of which 334 belong to one genus,
Selaginella^ while another, Lycopodium^ has 94. Like the
Equisetineae they are abundant in a fossil condition, and it is
very evident that these ancient forms were, many of them,
enormously larger than their living representatives, and more
complicated in structure. The living species are mainly tropical
in their range, but Lycopodium has a number of species common
in northern countries, and a few species of Selaginella^ e.g, S.
rupesiriSy have a wider range ; but the great majority of the
species are found only in the moist forests of the tropics. The
gametophyte of the homosporous forms is known only in Lyco-
podium^ and this only within a comparatively short time. Our
knowledge of it is based mainly upon the important researches
of Treub,^ but these have been added to by Goebel ^ in the case
of Z. tnundatum. The gametophyte in its earliest condition, so
far as is certainly known, develops chlorophyll, and this con-
dition may be permanent, e,g. L, cemuuniy but other forms have
a chlorophylless prothallium, and are saprophytic in habit, Jike
Ophioglossum. The germination of these forms is at present
unknown.

The sporophyte has the axis strongly developed, and the
leaves, though usually numerous, are simple in structure and
generally small. The genera are all homosporous except
Selaginella, which is very markedly heterosporous, and has the

» Baker (2). ^ Treub (2). « Goebel (18).

Fig. 243.— Part of a fruiting plant of Lycopodinm clavatum (L.X ^ | ; B, sporophyll, with sporangium
{sf) of L. dendroideum (Michx.)> X 13 ; C, cross<section near the base of an aerial shoot of L.
dtndreidtu9Hy xia.

CHAP. XIV L YCOPODINE^ 463

gametophyte very much reduced and projecting but little beyond
the spore wall.

Classification

\ A. HomosporecB

j I. Roots always present ; sporangia alike, simple, in the

^ axils of more or less modified leaves, which may form a distinct

jl strobilus, or may be but little different from the ordinary ones

f both in form and position ; prothallia either green or colourless,

■ monoecious.

I Order /. Lycopodiace^

\ Genera 2. — (i) Lycopodium ; (2) Phylloglossum

I II. Roots absent; vegetative leaves much reduced {Psi-

\ lotum) or well developed ; sporophylls petiolate, bilobed ; spor-
f angia plurilocular ; gametophyte unknown.

f Order II. Psilotace^

Genera 2. — (i) Psilotum ; (2) Tmesipteris
£ B. HeterosporecB

Characters those of Order I., but spores always of two kinds.

Order III Selaginellem
Genus i. Selaginella
' The LycopodiacecB

The Lycopodiaceae include the two genera Lycopodium and
Phylloglossuvty the latter with a single species, P. Drummondii,
The gametophyte is known in a number of species of Lycopodium^
but as yet is quite unknown in Phylloglossum, The first in-
vestigator who succeeded in obtaining the germination of the
spores was De Bary,^ who studied the earliest stages in the
germination of L, inundatum, but was unable to obtain the later
ones. About fifteen years later Fankhauser found the old

1 De Bary (I).

464 MOSSES AND FERNS chap.

prothallia of L, annotinum} but our principal knowledge of the
prothallium and embryo is due to the labours of Treub,*
who has most thoroughly examined several tropical species of
Lycopodium, Goebel ^ succeeded in finding a number of pro-
thallia of L. inundatum which corresponds very closely to L.
cemuuffty the first species examined by Treub.

The germination of the spores is much like that of the
homosporous eusporangiate Ferns. The tetrahedral spores con-
tain no chlorophyll, but this develops before the first division
wall is formed. This may be either vertical or horizontal, or
more or less inclined. The two primary cells are nearly equal
in size, but one of them appears to normally remain undivided.
The other enlarges and becomes divided by an oblique wall
(Fig. 244, A), and functions for some time as an apical cell,
from which segments are cut off alternately right and left.
Usually each segment is then divided by a periclinal wall into
a central and a peripheral cell. Up to this point the germina-
tion of L. cernuum corresponds exactly with De Bary's obser-
vations upon L, inundatum. The ovoid body formed at first
Treub calls the " primary tubercle," and this does not develop
directly into the complete prothallium, but the apical cell ceases
to form two rows of segments and elongates so as to produce a
filament in which for a time only transverse walls are formed
(Fig. 244, B). The base of this filamentous appendage, how-
ever, later develops longitudinal walls and forms a thickened
cylindrical mass, which is the beginning of the prothallium body.
Sometimes, but not usually, a second filamentous outgrowth is
formed from the primary tubercle, which may produce a second
prothallial body.

The growth of the prothallium proper does not seem to
show a definite meristem, but at the summit are produced a
number of leaf- like lobes which seem to arise in acropetal
succession, and the growth may be considered, in a general
way at least, as apical. The individual lobes are usually ti^'o
cells thick, and like those of Equisetum show a definite two-
sided apical cell. This apical growth later disappears and all
trace of it is lost in the older lobes. Root-hairs are produced
only in small numbers from the cylindrical prothallium body,
and are usually entirely absent from the primary tubercle, whose
peripheral cells are always occupied by an Endophytic fungus

1 Fankhauser (i). « Treub, M. (2). ' Goebel (18).

LYCOPODINEJE 465

which Treub refers probably to the genus Pythtum, We have
seen that similar fungus mycelia occur in the chlorophylless
prothallium of Botrychiunty and Goebel found the same in L.
inundatum. While in the primary tubercle the fungus occupies
the lumen of the cells, as it penetrates into the body of the
prothallium it confines itself mainly to the intercellular spaces,
where its growth causes more or less displacement of the
cells. It does not, however, seem to penetrate into the meri-
stematic tissues at the summit.

The fully-grown prothallium of L, cernuum is a small upright
cylindrical body, seldom, apparently, exceeding about two mm.
in height. The base is more or less completely buried in the
ground, and contains but little chlorophyll. The summit is
surrounded by the lobes already spoken of, and these have
somewhat the appearance of leaves crowning a short stem. The
whole structure of the prothallium recalls in some respects that
of Equisetuffty and like that resembles the young plants of
Anthoceros fusiformis or A. punctatus.

Besides the type of prothallium found in Z. cernuum^ with
which Z. inundatum closely agrees, Treub has also studied the
very different prothallium of L. phlegmariay and others of similar
habit. These are only known in their mature condition, in which
they are saprophytes, growing in the outer decayed layers of
bark upon the trunks of trees. In this condition they are
extremely slender branched structures, totally different from
those of Z. cernuum^ both in form and in the complete absence
of chlorophyll. Like the prothallia of many Hymenophyllaceae,
they multiply by special gemmae and apparently may live for
a long time. Like those of Z. cernuum they are always infected
by an endophytic fungus.

A third type of prothallium is that oi L. annotinum^ which
is also destitute of chlorophyll in its adult condition, but is com-
pact in form, more like that of Botrychium. Unfortunately in
this species, as well as the Phlegmaria type, the germination of
the spores is unknown, and it is still doubtful whether chloro-
phyll is developed at first, as in Z. cernuum.

The Sexual Organs

The prothallia of all the forms investigated are monoecious,
and the sexual organs not arranged in any definite order.

2 H

466

MOSSES AND FERNS

The sexual organs of all investigated species of Lycopodium
are very similar, and closely resemble those of the eusporangiate
Ferns and Equisetum, As in these forms the antheridium
mother cell divides first by a periclinal wall into an outer and
inner cell, the latter giving rise immediately to the sperm cells.
In the outer cell the divisions are much like those in Maratiia^
but the opercular cell does not become detached as in these, but
is broken through as in the Poly pod iaceae. In L, phlegmaria the
outer wall is often in places double, as not unfrequently is the

Fig. 244. — A, B, Very young prothallia of Lycopadiuvt cemuum (L.). A, x 250 ; IJ, x 200. P.
Primary tubercle ; C, an older prothallium of the same species with the first antheridium (<J),
X7S ; D, a fully-developed prothallium (/r) with the young sporophyte attached, X la ; /c, proco-
corm ; R, primary root ; E, section through an antheridial branch of the prothallium of L. ^kUg-
tnaria (L.), showing antheridia ( <$ ) in different stages of development ; par, a paraphysis, x 180 ;
F, surface view of the top of an antheridium of the same species ; o, opercular cell, X x8o ; G. a
spermatozoid, X4to ; H, section of the archegonium of the same species, x 180 (all the figizre;*.
after Treub).

case in the Ophioglosseae. The spermatozoids are almost
straight oblong bodies with two cilia, like those of the Bryo-
phytes (Fig. 244, G). The vesicle, which usually remains
attached to the spermatozoids of most Archegoniates, here is
almost always free, and often remains within the sperm cell after
the escape of the spermatozoids.

The archegonium in its development corresponds essentially
with that of the other Pteridophytes. The basal cell appears

XIV LYCOPODINEjE 467

to be always wanting, as is usually the case in Equisetunty and
a definite layer of cells surrounding the venter is also not
usually evident. Z. phlegmaria is especially noteworthy on
account of the large number of canal cells, which range in
number from three to five. Treub also states that the nucleus
of each canal -cell may divide again, so that in regard to the
number of canal cells L, phlegmaria^ of all Pteridophytes,
approaches most closely to the Bryophytes. Another peculi-
arity of this species is the presence of numerous paraphyses
among the sexual organs, in which respect it ^also offers an
analogy with many Bryophytes. .

The Embryo ^

Treub has traced the development of the embryo in Z.
pitlegmaria through all its stages, and has shown that Z.
cernuum corresponds closely to it, and Goebel's ^ investigations
upon Z. inundatum show that this species does not differ
essentially from the others. The first division in the embryo
is transverse, and of the two primary cells the one next the
archegonium remains undivided, or divides once by a transverse
wall and forms the suspensor, which is characteristic of all
investigated Lycopodineae, while the lower cell alone gives rise
to the embryo proper. In the embryonal cell the first wall is
a somewhat oblique transverse one, which divides it into unequal
cells. In the larger of these a wall forms at right angles to the
primary wall (Fig. 245, A), and this is soon followed in the
smaller cell by a similar one, so that the embryo is divided into
quadrants. Of these the two lower form the foot, while of the
upper ones in Z. pitlegmaria^ the one formed from the larger
of the two primary cells {moitii convexe of Treub) produces the
cotyledon, the other the stem apex. The primary root, which
in Lycopodium arises very late, originates from the same quad-
rant as the cotyledon.

In Z. cernuum y while the early divisions correspond exactly
with those of Z. phlegmaria^ the further development of the
embryo shows some noteworthy differences. As in that
species, the two lower quadrants form the foot, which here
remains completely buried within the prothallium. From the
upper part of the embryo is next developed what Treub calls

» Treub (2). * Goebel (18).

468

MOSSES AND FERNS

the " protocorm." This is a tuber-like organ (Fig. 244, D, pc),
from which the leaves and stem apex are subsequently
developed. The cotyledon arises from the summit of the

Fic. 345.— Embryogcny of Lycopodium phlegmaria (L.) (after Treub). */, Stem ; cot, cotyledoa ;
susp, suspensor. A, X 315 ; B, x 235 ; C, x 235 ; D, x 175.

protocorm, and is followed by a number of secondary leaves
which form successively from a group of meristematic cells,
which usually develop into the permanent apex of the stem.

LYCOPODINE^E 469

About the time that the stem apex becomes recognisable as
such, the first root appears as a surface outgrowth of the
protocorm, and strictly exogenous in origin. Not infrequently
the end of the primary root gives rise to a tubercle similar to
the protocorm.

An interesting case was seen by Treub, where, apparently
by a longitudinal division of the young embryo, two embryos
were formed, much as is normally the case in some Gymno-
sperms.

On comparing the two types of embryo found in L,
phlegtnaria and L. cernuum^ the main differences are the almost
complete absence of the protocorm and greater development of
the suspensor in the former. L, tnundatum, as might be expected,
corresponds closely in the structure of the young sporophyte
with L, cemuunt.

Corresponding with the late appearance of the roots is the
late development of the vascular bundles, which, according to
Treub, are often quite absent from the cotyledon and even
occasionally from the second leaf. The protocorm of Z.
cemuum and L, inundatum Treub regards as the remains of a
primitive structure originally possessed by the Pteridophytes,
which replaced the definite leafy axis found in the more
specialised existing forms.

The Sporophyte

In all species of Lycopodium the sporophyte possesses an
extensively branched stem, which may be upright, as in L,
cemuuMy or extensively creeping, as in L, clavatum and other
species, where the main axis is a more or less completely
subterranean rhizome with upright secondary branches. In
the Tropics some species are epiphytes. The leaves are
always simple, and of small size. Each leaf has a single
median vascular bundle, which does not extend to the apex.
The arrangement of the leaves is usually spiral, and they are
uniformly distributed about the stem, and all alike ; but in a
few species, e,g. L. complanatutn, they are of two kinds and
arranged in four rows, as in most species of Selaginella. The
branching of the stem is either dichotomous or monopodial.
The roots, which are borne in acropetal succession (Bruchmann
found also in Z. inundatum adventive roots), branch dichotom-

470

MOSSES AND FERNS

CHAP.

ously, like those of Isoetes. The sporangia are borne singly, in
the axils of the sporophylls, which may differ scarcely at all
from the ordinary leaves (Z. selago^ L. luciduluni), (Fig. 248),
or the sporophylls are different in form and size from the other
leaves and form distinct strobili, which are often borne at the
end of almost leafless branches (Fig. 243).

None of the investigated species of Lycopodiutn show a
definite initial cell at the apex of the stem, and Treub ^ was

Fig. 246.— Longitudinal section of the stem apex o{Lycopodium lucidulum (Michx.), X 30. j^, Voonc
sporangium ; B, longitudinal section of the young sporangium of the same species, x 2x5.

unable to determine positively whether such a one exists in the
embryo. In Z. /A/^^w<3:r/a ^ he describes and figures embryos,
where a single prismatic apical cell is apparently present, but
in others the presence of such a cell was doubtful, and in Z.
cernuum in no case did he find any evidence of a single initial.
The vegetative cone of the mature sporophyte is usually
broad (Fig. 246) and only slightly convex. Its centre is
occupied by a group of similar initial cells, which in Z. selago^

* Treub (2), vol. v.

5 Treub, U. PI. XXIX.

L YCOPODINE^

471

according to Strasburger,^ usually show two initials in longi-
tudinal section (Fig. 247, t). From these initials are cut ofif
lateral segments which, by further periclinal and anticlinal walls,
produce the epidermis and cortex, and secondarily the leaves.
Periclinal walls also are formed from time to time in the initial
cells, by which basal segments are cut off, which produce the
large central plerome cylinder.

The leaves arise as conical outgrowths near the stem apex,
and owe their origin to the three or four outer cell layers of the
growing point. The separation of the epidermis does not occur

Fig. 2^T.—Lycopodium selago (L.). A, Longitudinal section of the stem apex, Xiao; /^/^ young
leaves ; /, ;', initial cells ; //, plerome ; B, surface view of the stem apex, showing the group of
initial cells, x 260 ; C, longitudinal section of the root-tip ; d, dermatogen ; pb^ periblem ; //,
plerome ; cal^ calyptrogen ; A, A, root-hair initials, X 120 (all the figures after Strasburger).

until the leaf has formed a conspicuous conical protuberance.
The differentiation of the procambium in the young leaf begins
earjy, and the strand joins the central procambial cylinder of
the stem, which, however, is quite independent of the leaf-
traces. Each young leaf-trace joins an older one at the point
of junction with the stem cylinder, and thus the complete stem
possesses two systems of vascular bundles, the strictly cauline
central cylinder, and the system of common bundles formed by
the united leaf-traces.

The first elements of the vascular bundles to become

* Strasburger ( 10), p. 240.

472 MOSSES AND FERNS chap.

recognisable are spiral tracheids, both in the stem and leav'es,
and these are followed in the former by the much wider
scalariform tracheids that occupy the central part of the
tracheary plates in the fully-developed bundles.

The fully -developed central cylinder of the stem^ is un-
doubtedly to be considered as a group of confluent vascular
bundles or as gamostelic. The oval or nearly circular cross-
section (Fig. 243, C) is sharply separated from the surrounding
ground tissue by a clearly-marked endodermis, within which is
a pericycle which may be only one cell thick, but is usually
several-layered. According to Strasburger * this pericycle does
not properly belong to the central cylinder, but is of cortical
origin. The cutinised band ("radial folding") of the endo-
dermal cells is only observable in the younger stages, as later the
whole wall of the endodermal cells becomes cutinised." This
cutinisation extends also through a number of the succeeding
cortical layers. The rest of the cortical region is in most
species occupied by elongated sclerenchyma cells, with no
intercellular spaces.

The central vascular cylinder contains, as is well known,
alternating, usually transversely placed, tracheary plates, alter-
nating with phloem masses, and surrounding these a varying
amount of parenchyma. In upright species the tracheary
plates are often more or less completely confluent, and in
cross-section have a somewhat star -shaped outline. In the
dorsiventral stems the tracheary plates are quite separate
and perfectly transverse in position. Their outer angles are
occupied by the small primary spiral or annular tracheids,
from which the centripetal formation of the large scalariform
elements proceeds exactly as in the leptosporangiate Ferns.
The mass of tracheary tissue is compact, and contains no
parenchymatous elements. According to Strasburger* the
oblique end walls of the large tracheids show the same
elongated pits as the lateral walls, but in no cases could any
communication between adjacent tracheids be demonstrated.
Each tracheary mass is surrounded by a single layer of
parenchyma, whose inner cell walls show bordered pits, like
those of the adjacent tracheids.

* Russow (i), p. 128 ; De Bary (3), p. 281 ; Strasburger (11), vol. iii. p. 458.

' Strasburger, /.r. p. 460. • Strasburger, Lc. ; Van Ticghem (5), p. 553.

* Strasburger, l.c, p. 459.

LYCOPODINE^ 473

The phloem masses are, in the arrangement and develop-
ment of the parts, very like the xylem, and the formation
of the sieve -tubes begins at the outer angles and proceeds
centripetally. The fully-developed sieve-tubes appear almost
empty, and the small sieve -plates are poorly developed and
difficult to demonstrate.

Where the branching is monopodial, the young branches
arise laterally close to the growing point, but without any
relation to the leaves. Where, however, as in L. selago} there
is a genuine dichotomy, it is inaugurated by an increase in the
number of initial cells, which is then followed by a forking of
the apex of the plerome cylinder, and the two resulting branches
are exactly alike. Intermediate conditions between a perfect
dichotomy and true monopodial branching occur. In these
there is a true dichotomy, but one branch is stronger than the
other, and continues as the main axis, while the weaker one is
pushed to one side and looks like a lateral shoot. Bruchmann ^
has described certain "pseudo-adventive '* buds, which are young
branches arrested in their development at a very early stage,
which may later develop. Strasburger^ has found adventive
buds in L. aloifoliuniy L. verticillatum, L. taxifolium, and Z.
reflexuniy which possibly may be of the same nature.

The Leaf

The leaves of all species of Lycopodium are relatively small,
and are usually lanceolate in outline with broad sessile base.
The margins of the leaves are often serrate, and in all cases
the leaf is traversed by a simple midrib, which, as already
stated, does not reach to the apex. Their arrangement varies,
even in the same species, and upon the same shoot. Thus in
L. alpinum * the leaves are regularly arranged in pairs which
arise simultaneously ; in L. selago they are usually in true
whorls of four or five. The latter, however, often shows a
spiral arrangement of the leaves, with a divergence of two-
ninths, less often two-sevenths.

The structure of the vascular bundle of the leaf is simple.*
It is concentric in structure, with the central part composed
of a small number of spiral and annular tracheids, with the

* Strasburger (lo), p. 242. ' Luerssen (7), vol. vii. p. 627. * Strasburger (7).
* Hegelmaier (i), p. 815. * Strasburger (11), vol. iii. p. 461.

474 MOSSES AND FERNS chap.

peripheral portion made up of parenchyma, with a circle of
scattered narrow sieve-tubes. A definite endodermis cannot
be demonstrated. In the species with the leaves all alike both
surfaces bear stomata, but in those with decussate leaves the
greater part of the upper surface is destitute of them.

T/te Root

The roots of Lycopodium arise, as in other Pteridophytes, in
acropetal succession, but with no relation to the position of
the other organs. According to Bruchmann adventive roots
may arise in L, inundatum^ but they have not been observed
in other forms. Z. selago ^ may serve to show the characters
of the root in the genus. The meristem of the apex is clearly
dififerentiated into the initials of the dififerent primary tissues
(Fig. 247, C). The dermatogen {d) completely covers the apex
of the growing point as a single layer. The periblem {pb') is
three cells thick ; the plerome {pt) terminates in a group of
special initials. As in the stem, the plerome alone forms the
central cylinder, the periblem giving rise only to the cortex,
and the, structure of the mature root corresponds closely to
that of the stem, except for the presence of the root-cap, which
has its own initial group of cells (calyptrogen, cat). From the
older dermatogen cells are derived, by special walls, the mother
cells of the root-hairs (A).

Van Tieghem ^ states that the secondary roots arise from
the pericycle instead of from the endodermis, as in other
Pteridophytes, but Strasburger claims that the so-called peri-
cycle of Lycopodium is really cortical, and does not belong
properly to the central cylinder, so that this difference is only
apparent. The endodermis itself is not readily recognisable
on account of the complete cutinisation of the walls.

The origin of the root-hairs is somewhat peculiar. From
the base of each dermatogen cell a wedge-shaped cell is cut
off (Fig. 247, C, //), and this afterwards is divided into two
similar cells, each of which grows out into a unicellular hair.
Thus the root-hairs are found in pairs.

The roots always normally branch dichotomously, as in
IsoeteSy and the successive divisions usually are in planes at
right angles to each other. As in Isoetes^ the process is in-
* Strasburger (10), p. 259. * Van Tieghem (5), p. 553.

lycopodineje:

475

augurated by a broadening of the apex of the root, which is
followed by a forking of the plerome and a subsequent division
of the other histogenic tissues.

The structure of the mature root^ in L. clavatum, L,
alpinum, and most species examined, is much like the stem.
The hexarch to decarch fibrovascular cylinder is radial in
structure, the xylem plates often
united at the centre, so that
in cross-section they present a
more or less regular stellate
form. In L. selago and L, in-
undatuni^ according to Russow,^
the xylem is diarch and the two
masses united into a single one,
which is crescent-shaped in sec-
tion, with the phloem occupying
the space between the extremi-
ties. As in the stem the primary
tracheids are narrow annular
and spiral ones, and the large
secondary ones scalariform.

Gemmce

Special bulblets or gemmae
are formed regularly in a number
of species of Lycopodium^ and
have been the subject of several
special investigations.^ These
in L, lucidulum (Fig. 248, A. ^)
are flattened, heart - shaped
structures composed of several
thickened fleshy leaves, and
formed apparently in the axils
of somewhat modified stem

leaves, from which they readily separate when fully grown. The
axillary origin of the bulblets is only apparent ; they are really,
so far as can be determined, similar in origin to the ordinary

* Russow (1), p. 150 ; Van Tieghem, ** R^cherches sur la symmetrie de la structure
dans les Plantes vasculaires" {Ann, Sc. not., ser. 5, No. xiif.).

* Russow (i). " Hegelmaier (i) ; Slrasburger (7) ; Cramer (i).

Fig. 248. — A, End of a shoot of Lycopodium
iuciduium (Michx.), with gemmae {k) and
sporangia (x/X Xa*> ^t ^ single bulblet,
X 4 ; C, germinating bulblet of L. selago
(after Cramer), X 4 ; r, the primary root.

476 MOSSES AND FERNS chap, xiv

branches, and formed without any relation to the leaves.
Before the bulblet becomes detached, the rudiment of a root
can be made out at the base, and as soon as it falls off and
comes in contact with the earth the root begins to grow and
fastens the bulblet to the ground (Fig. 248, C). The axis of
the bulblet, which at first is very short, rapidly elongates, and
the leaves formed up it have the characters of the ordinary
ones. As the leafy axis develops the fleshy leaves of the
bulblet lose their chlorophyll completely and finally decay.

Hegelmaier^ describes mucilage ducts in the stem and
leaves of L, inundatum and some other species, which are not
unlike those found in Angiopteris,

The Sporangia

The most recent and accurate account of the structure and
development of the sporangia of the Lycopodineae is that given
by Professor Bower in his recent memoir upon this subject*
His investigations include a number of species of Lycopodiutfiy
and the following account is taken mainly from his memoir.
The results of his investigations show that there is much more
variety shown than was before supposed, both in the form of
the sporangium itself and in the mode of origin and number of
the archesporial cells.

In Z. selago the sporangium originates upon the upper
surface of the sporophyll close to its base, and in radial section
the young sporangium appears to originate from a single cell ;
but this is really only one of a transverse row of cells, all of
which participate in its formation. Each cell of this primary
row divides first into a large central cell (Fig. 249, C, x) and
(in radial section) two peripheral ones. The central cell next
by successive periclinals forms a row of three cells, of which the
middle one is the archesporium, which, judging only from radial
sections, seems to consist only of a single cell ; but comparing
with the radial section a tangential one, it is seen that the
archesporium really consists of a row of similar cells (Fig. 249,
F). The growth in the upper part of the sporangium is
stronger than below, so that a distinct, although short stalk is
formed. The archesporial cells rapidly divide, but show little

* Hegelmaier (i).
* Bower (15) ; also Goebel (3), Bot. Zeit. 1880, p. 561 ; Sadebeck (6), p. 313.

Fig. 249.— a, Plant of Phylhglostum Drummondii (Kunze), X about 3 (after BertrandX *p% Spor-
angia ; R, roots ; Tl, protocorm ; T^, secondary protocorm ; B, longitudinal section of the young
strobilus of the same, showing the initial cell (1), young leaves (r, TO. and young sporangium (x/X
X 240 ; C-£, young sporangia of Lyco/Ktdium ulai^o^ radial sections, X 325 ; F, tangential section
of the same ; G, radial section of young sporangium of L. clavatum (Figs. B-G after Bower).

478 MOSSES AND FERNS chap.

regularity in the divisions. All of the resulting cells separate
and produce four spores in the usual manner. The wall of the
mature sporangium consists regularly of three layers of cells, of
which the innermost is the tapetum. The tapetum bounding
the lower part of the archesporium is derived from the cushion-
like group of cells below it, to which Bower gives the name
" sub-archesporial pad." The tapetum does not, apparently,
become disorganised, as in most Ferns and Equisetum, but
remains as part of the sporangium wall. The fully-grown
sporangium, as in all species of LycopodimUy is kidney-shaped.

Among the numerous other species investigated by Professor
Bower, L, clavatum represents the type most widely removed
from Z. selago. The differences between the two are sum-
marised by Professor Bower ^ as follows.

" I. The sporangium is similar in position and in general
form to that of Z. selago^ but its body is more strongly
curved.

" 2. The archesporium here consists of three rows of cells^
each row being composed of a large number (about twelve)
of cells ; thus the extent of the archesporium is much greater
than in Z. selago, occasional additions to it seem to be made
by cells cut off periclinally from the superficial cell at an early
stage.

" 3. The tapetum is similar in origin to that in Z. selago.

" 4. The sub-archesporial pad is much more developed, and
is at times extended as processes of tissue which penetrate the
sporogenous mass for a short distance.

" 5. The stalk of the sporangium is much shorter and thicker
than in Z. selago,

" 6. Arrested sporangia are frequently present, and may be
found either at the base or apex of the strobilus.

" 7. Z. inundatum may be looked upon as an intermediate
link between the type of sporangium of Z. selago and that of
Z. clavatum, both as regards form of the sporangium and
complexity of the archesporium."

Phylloglossum

The other genus of the Lycopodiaceae contains but the single
species P, Drumtnondiiy from Australia This curious and

^ Bower (15), p. 521.

XIV LYCOPODINE^ 479

interesting little plant has been carefully investigated by-
Bower ^ and Bertrand,^ and the former regards it as the most
primitive in structure of all the living Pteridophytes. Unfor-
tunately the gametophyte is almost entirely unknown,^ but the
structure and development of the sporophyte have been carefully
studied by the above writers.

The sporophyte resembles in an extraordinary degree the
young sporophyte of Lycopodium^ especially Z. cernuunt. It
grows from a small tubercle (protocorm), which is regarded as
homologous with the same structure in the embryo of Lyco-
podium. This protocorm in small plants produces only sterile
leaves — from four to seven — and a small number of roots, often
only a single one. In more vigorous plants a smaller number
of sterile leaves is formed, but the apex of the protocorm grows
into an elongated axis, bearing a single small strobilus at the
apex (Fig. 249, A). The structure of the latter is essentially as
in Lycopodium. The roots are produced exogenously, as in
the Lycopodium embryo, and are in structure much the same.
All of the tissues are very simple, and none of the organs show
a single apical cell, except possibly the apex of the strobilus,
where such a single initial seems to be sometimes present
(Fig. 249, B, i). At the end of the growing season a new
protocorm is formed. This arises directly from the apex of
the old one, where no strobilus is developed, but in the latter
case grows out upon a sort of peduncle from near the base of
one of the leaves. The development of the sporangia is essenti-
ally the same as in Z. selago (Fig. 249, B).

The anatomy of the vegetative organs has been carefully
studied by Bertrand,* and corresponds closely to that of Lyco-
podium, but the tissues are simpler. In the axis which bears
the strobilus there are about six xylem masses arranged in a
. circle, but there is no definite endodermis limiting the central
cylinder. The root-bundle is diarch.

Bertrand^ states that M. L. Cri^ found that the spores
germinated readily, and produced a colourless prothallium like
that of the Ophioglosseae, both in form and in the structure of
the sexual organs, but that the spermatozoids are biciliate.

^ Bower (5). " Bertrand (3).

' The observations of Cri^ quoted by Bertrand, were not accessible to the
writer,

* Bertrand (3). * Bertrand, Lc, No. 34, pp. 221, 222.

48o MOSSES AND FERNS chap.

These observations have not yet, however, been confirmed by
other observers.

The dififerences between Phylloglossum and Lycopodium do
not seem sufficient to warrant the establishment of a separate
family, the Phylloglosseae, as Bertrand proposes.

The PsilotacecB

The Psilotaceae include the two evidently related genera
Psilotum and Tmesipteris^ the former with two species,^ the
latter with but a single one. All the species are tropical or
sub-tropical, Psilotum being found in all the warmer parts of
the world ; but Tmesipteris is confined to Australia, New
Zealand, and parts of Polynesia. The prothallium is quite
unknown in both genera, but the development and anatomy
of the sporophyte of both are now pretty well known. The
sporophyte,^ which in its mature condition is quite destitute
of roots, grows either upon earth rich in humus {Psilotum
triquetrum)y and is evidently more or less saprophytic, or
it may be an epiphyte. Tmesipteris grows upon the trunks
of tree-Ferns, and Bertrand states that it is a true parasite,
which, however, like Viscum or Phorodendron^ has not entirely
lost its chlorophyll. The plant always consists of two parts,
a lower portion consisting of branched root-like rhizomes, which
take the place of roots, and aerial green branches which ramify
dichotomously. The branching is especially marked in
Psilotum^ much less so in Tmesipteris, The leaves are small
and scale-like in Psilotum^ larger and lanceolate in Tmesipteris,
The sporangia (or synangia) are bilocular in the latter, trilocular
in Psilotum^ and in both cases borne upon a small bilobed
sporophylL

The development of the sporophyte has been carefully
studied by Solms-Laubach,* who discovered that it multiplied
rapidly by means of small gemmae (Fig. 251, k) produced in
great numbers upon the subterranean shoots. These buds or
bulblets are small oval bodies, but one cell in thickness, and
showing usually a definite two-sided apical cell. Their cells
are filled with starch, and they sometimes remain a long time

* Baker (2). * Bertrand (i, 2); Solms-Laubach (1); Bower (15).

^ Solms-Laubach (i).

LYCOPODINE^

481

dormant. These buds may produce others, but usually from
each one is produced one, or sometimes more, elongated shoots,
which develop into subterranean branches like those from
which the bud was originally produced. The young plant

Fig. 250.— Part of a vigorous plant of Psiiotum triquetrum (Sw.), about \. u, tt, Subterranean
shoots ; a, a, the bases of aerial branches ; sy, synangia ; B, branch with two mature synangia,
slightly enlarged : C, a single opened synangium, showing the two lobes of the sporophyll below
it (after Bertrand).

arising from the gemma is at first composed of uniform
parenchyma, but in the later formed portions a simple vascular
bundle is finally developed. No definite apical cell can be
detected in the earlier stages, but later each branch of the
rhizome shows a pyramidal initial cell, much like that in the

2 I

482

MOSSES AND FERNS

CHAP.

Ferns, but less regular in its divisions, and it is not possible to
trace back all the tissues with certainty to this single cell.
The branching is a true dichotomy, but is not brought about
by the division of the original apical cell, but this becomes
obliterated previous to the formation of the two branches, and
two new initial cells are formed quite independently of it^

The tissues are very simple. In the subterranean stems
the bulk of a section is composed of parenchyma, while the

Fig. 35J,—Pst7civm trigueirum (Sw.). A, Fragment of a subterranean shoot with a young gemma
{k\ xi3o; B, longitudinal section of the apex of a subterranean shoot, X185; C, transverse
section of the apex of a subterranean shoot in the act of forking ; jr, jr, the apical cells of the two
branches, x 185 (all figures after Solms-Laubach).

vascular bundle is very similar to that of the roots of the
Ferns. The bundle is diarch, and the two xylem masses are
confluent at the centre. In the aerial shoots the cross-section
of the vascular cylinder shows a central mass of thick-walled
Hgnified cells about which the triarch to octarch xylem forms
a continuous ring.^ The phloem is poorly developed, and the
xylem is mainly composed of small thin-walled scalariform
tracheids. In Psilotum the leaves have no vascular bundle, in
Tmesipteris a single bundle traverses the leaf, as in Lycopodium,

' Solms-Laubach (i), p. 154. ^ Russow (i), p. 131.

LYCOPODINE^

483

The Sporangia

There has been much disagreement as to the morphological
nature of the sporangiophores of the Psilotaceae. The two
chief views are the following.^ (i) That the whole sporangio-

FiG. i^i.—Tmesipteris tannensis (Bernho). A, Radial section of the young sporangiophore, x 113 ; 47,
the young synangium ; B, similar section of an older sporangiophore, Xiza. The archesporial
cells are shaded. C, Fully-developed s>'iiangium, showing its position between the two lobes of
the sporophyll, x 3 ; D, a longitudinal section of the synangium, showing the two loculi (all the
figures after BowerX

phore is a single foliar member ; (2) that it is a reduced axis
bearing a terminal synangium and two leaves. The recent
very careful researches of Bower upon the origin of the
sporangiophore and synangium confirm the former view. He
describes the development in Tmesipteris as follows. " The
apical cone of the plant is very variable in bulk. ... In the

* Bower (15), p. 541.

484 MOSSES AND FERNS chap.

large as well as the small specimens a single initial is usually
present, but its segmentation does not appear to be strictly
regular, and it is difficult to refer the whole meristem to the
activity of one parent cell. . . . When a leaf or sporangio-
phore is about to be formed, certain of the superficial cells
increase in size, and undergo both periclinal and anticlinal
divisions so as to form a massive outgrowth, the summit of
which is occupied, as seen in radial section, by a single lai^er
cell of a wedge -like or prismatic form. ... In these early
stages I find it impossible to say whether the part in question
will be a vegetative leaf or a sporangiophore, and even when
older it is still a matter of uncertainty. . . . Those which are to
develop as sporangiophores soon show an increase in thickness,
while they grow less in length ; an excrescence of the adaxial
surface soon becomes apparent (Fig. 252, A, sy\ in which the
superficial cells are chiefly involved. . . . The superficial cells at
first form a rather regular series, which may be compared with the
cells which give rise to the sporangia in Lycopodium davatum,
or in Isoetes : they undergo more or less regular divisions,
which, however, I have been unable to follow in detail : a band
of tissue some four or more layers in depth is thus produced.
About this period certain masses of cells assume the characters
of a sporogenous tissue : but though they can be recognised as
such by the character of the cells, it is extremely difficult to
define the actual limits of these sporogenous masses."

In Tmesipteris there are normally two masses of sporo-
genous tissue corresponding to the two loculi in the mature
synangium ; in Psilotum^ which correspond closely with Tmesi-
pteris in other respects, there are three. Whether additions are
made to the sporogenous tissue from cells outside the original
archesporium was not determined with certainty, but Professor
Bower thinks it not improbable. In Psilotum the young
archesporium is more clearly defined than in Tmesipteris^ and it
seems not unlikely that each sporogenous mass is referable to
the division of a single primary archesporial cell. In both
genera some of the sporogenous cells do not develop spores,
but simply serve for the nourishment of the others, as in
Equisetum.

The fully-developed synangium has the outer walls of the
loculi composed of a single superficial layer of large cells,
beneath which are several layers of smaller ones (Fig. 252, D).

XIV LYCOPODINEAl 485

The cells composing the septa are narrow tabular ones, with
firm woody walls marked by numerous pits. Occasionally the
septum is partially absent and the loculi are thus thrown more
or less completely into communication. The spores are usually
of the bilateral form, like the microspores of Isoetes, but may
also be of the tetrahedral type.

Bower regards the whole synangium as homologous with
the single sporangium of Lycopodiuni, and also calls attention
to its resemblance to the sporangium of Lepidodendron^ with
which the Psilotaceae also show remarkable resemblances in the
structure of the stem.

The Selaginellece

Unlike the Filicineae, the heterosporous Lycopodineae out-
number very much the homosporous forms, but all of the
former may be reduced to a single genus, Selagmella^ which
contains nearly three hundred and fifty species, and, except for
the presence of heterospory, approaches closely the genus
Lycopodiunty to which it is clearly not very distantly related.
The great majority of the species of Selaginella belong to the
Tropics, and form a characteristic feature of the forest vegeta-
tion of those regions. A few belong to the more temperate
parts of Europe and America, and a small number, e,g. S,
rupestriSy S. lepidophylla^ grow in dry situations.

The Gametophyte

Hofmeister ^ included Selaginella among the other Pterido-
phytes he studied, but he was unable to make out the earlier
stages of development of the prothallium. Later Millardet^
and Pfeffer ? made further investigations upon the same subject,
and added much to Hofmeister's account, but were also unable
to determine the earliest phases of germination. Belajeff* has
since given a clear account of the germination of the micro-
spores, but up to the present time the exact method of formation
of the female prothallium has remained doubtful. Recently a
further contribution has been made, to the subject by Heinsen,*
which, however, adds but little to our previous knowledge. The

1 Hofmeister (i). » Millardet (i). » Pfeffer, W. (i).

* Belajeff (I). « E. Heinsen (i).

486

MOSSES AND FERNS

CHAP.

account of the female prothallium given here is based upon the
writer's observations upon S, Kraussiana^ made from microtome
sections of spores treated with chromic acid and embedded in
paraffin.

The Microspores and Male Prothallium

The microspores of all species of Selaginella are small
and of the tetrahedral type. According to BelajefT^ they may
show either a distinct perinium, or the latter is not clearly

Fig. 253. — A, B, C, Three views of the young antheridium oi Selagtiulia Kraussiana (A. Br.X x 450 :
D, an older stage of the same, x 480 ; £, F, two views of an older antheridiAun of S. stoleni/erm.,
X480; G, spermatozoids of S, cuspidata (Sk.X x Z170 ; x, vegetative prothallial cell ; x, central
ceils (after Bel^geff).

separated from the exospore. The spores contain no chloro-
phyll, but much oil as well as solid granular contents^. At
the time that the spores are shed each one has already
divided into two very unequal cells, a very small lenticular cell
(Fig. 253, x) and a much larger one which, as in Isoetes^
becomes the single antheridium.

The first wall in the antheridium divides it into two equal
cells, each of which then divides into two others, a basal and

1 Belajeff(i).

XIV LYCOPODINEJ^ 487

an apical cell. The latter divides twice more, forming three
segments, so that the young antheridium at this stage
consists of eight cells arranged in two symmetrical groups.
Of the three segments formed in each apical cell, the
first and sometimes the second form periclinal walls, so that
a central cell (or two cells) is formed in each half of the
antheridium, not unlike what obtains in Marsilia^ and the
young antheridium consists now of two (or four) central cells
and eight peripheral ones. Belajeff states that the cell walls
do not show the cellulose reaction, and that they are later
absorbed. Where there are four primary central cells, these
by further divisions produce a single cell-complex, which, after
the disintegration of the peripheral cell walls, floats free in the
cavity of the spore. Where but two primary central cells are
formed, each produces a separate hemispherical cell mass.
Belajeff does not state the number of sperm cells formed.
The spermatozoids (Fig. 253, G) are extremely small and
closely resemble those of many Bryophytes, as well as Lyco-
podium. Like these they are always biciliate.

TIu Macrospore and Female Prothallium

The formation of the female prothallium begins while the
spore is still within the sporangium, and long before it has
reached its full size. The earliest division of the primary
nucleus was not seen, but it is undoubtedly much the same
as in Isoetes^ with which Selaginella closely agrees in the
development of the prothallium. The young macrospore is
quite transparent, and in the living condition is colourless and
shows plainly the single large globular nucleus. The youngest
stage, of which successful preparations were made, is shown in
Fig. 254, B. The spore here had reached about half its final
diameter, and was remarkable for the very small amount of
protoplasm it contained. This formed a very thin layer close
to the wall, much as in the embryo-sac of the Spermaphytes.
In this protoplasmic layer were embedded a number of some-
what flattened nuclei, but as yet there was no trace of cell
division. The central cavity appeared absolutely empty, and
doubtless in the living spore is filled with a watery fluid. The
relation of the nuclei to the primary nucleus could not be
traced, but in all probability it is the same as in Isoeies. In

488

MOSSES AND FERNS

somewhat older st?iges (Fig. 254, A) the nuclei were more nearly
globular in outline, and were more numerous at the apex of

per.

JB.

Fig. 2S4.—Seiag^tfte//4i Kraussiana (A. Br.). A, Section of the upper part of a macrospore still within
the sporangium, shortly before the first cell-formation, X 525 ; B, a somewhat earlier stage, show-
ing the very thin protoplasmic layer lining the wall, with the free nuclei (»X ^ S^S > C, transverse
section through the apex of the macrospore, showing the first cell-formation, X 570.

the spore, where the protoplasmic layer lining the wall was
also noticeably thicker. Shortly after this the first cell division

XIV

L YCOPODINEjE

489

occurs, and this takes place in a manner identical with that
found in Isoetes, or in the endosperm - formation of most
Spermaphytes. Fig. 254, C shows a cross-section of the apex
of the spore shortly after the first cell walls are complete.
The extremely regular hexagonal form of the cells toward
the centre of the prothallium is very noticeable. At the
margin, and below, the cells are larger, and often contain
several nuclei.

The cell -formation does not extend at this stage to the
base of the spore, as in Isoetes, but is confined to the apex,
where a definite cellular body is formed. This is three-layered

^^?^2^^^^^^^^^?^

Fig. 255. — Selaginella Kraussiana (A. Br.). A, Longitudinal section of a nearly ripe macrospore,
with the prinuuy prothallium (/r) complete, but still showing a large vacuole in the centre of the
spore, X 65 ; B, similar section of a younger stage, before the diaphragm has been differentiated,
X 400 ; n, nuclei.

in the middle, but at the margins but one cell in thickness.
The lower cells have the walls which are in contact with the
spore- cavity much thickened at a later stage, and thus is
formed the diaphragm which is so conspicuous in most species,
and which led Pfeffer to suppose that the first division in the
young prothallium was by a cell wall which separated the
prothallium proper from the lower part of the spore, in which
later the " secondary endosperm " is formed.

Scattered through the protoplasm of the spore-cavity are
numerous very small nuclei. The protoplasmic layer becomes
rapidly thicker (Fig. 255, A), and finally completely fills the

490

MOSSES AND FERNS

cavity of the spore. The thickenings upon the outer spore-
coat are very evident even before the primary nucleus divides,
and they increase rapidly in size, as the spore develops. A
very casual examination suffices to show that the tapetal cells
of the sporangium here play a most important part, not only
in the development of the spore-coat, but also in the growth
of the prothallium. The rapid increase in the amount of
protoplasm in the spore during the growth of the prothallium,
as well as the growth of the spore itself, can only be accounted

Fig. 2s6.—Seleigintila Kraussiana (A. Br-X A, Nearly median section of a fiilly-devcl4)ed female
prothallium, showing the diaphragm {d\ X 180. One of the archegonia has been fertili^cdf and
the suspensor (tus) has penetrated through the diaphragm into the tissue below it ; B-E, develop-
ment of the archegonium, X 360 ; F, two-celled embryo, belonging to the suspea<M>r shown in A,
X 360 ; G, end of a suspensor with two-celled embryo (em)y X 360.

for by the activity of these cells, which are in close contact
with the spore, and show every evidence of being active cells,
through whose agency the materials are conveyed to the spore
for its further development.

The first archegonia begin to form shortly before the spores
are shed, and soon after, the exospore splits along the three
ventral ridges and exposes the central part of the prothallium.

XIV LYCOPODINE^ 491

This, like that of IsoeteSy is quite destitute of chlorophyll, and
is entirely dependent upon the food materials in the spore for
its further development. About this time also begins the cell-
formation in the part of the spore below the diaphragm (Fig.
256). This is simply a continuation of the same process by
which the apical tissue was developed, but the cells are larger
and more irregular.

. The archegonia are produced in considerable numbers, and
apparently in no definite order. Their development corre-
sponds with that of Lycopodium^ but the neck is very short,
like that of the Marsiliaceae, each row of neck cells having but
two cells. No basal cell is formed, and the central cell is
separated from the diaphragm only by a single layer of cells.
The neck canal cell (Fig. 256) is broad, like that of IsoeteSy
but the nucleus does not, apparently, divide a^ain. The egg
(Fig. 256, E) shows a distinct receptive spot, and the nucleus is
clearly defined. At this stage the diaphragm is very evident
and much thickened, so that the archegonial tissue of the
prothallium is very sharply separated from the nutritive tissue
below.

The Embryo

The first division in the fertilised ovum is transverse, and
as in Lycopodium the cell next the archegonium neck becomes
the suspensor. This in Selaginella is much more developed,
however, and grows at first more actively than the lower cell
from which the embryo proper arises. The upper part of the
suspensor enlarges somewhat, and forms a bulbous body, which
completely fills the venter of the archegonium. The suspensor
grows rapidly downward, penetrating the diaphragm and push-
ing the young embryo down into the mass of food cells which
occupy the space below it. The suspensor is very irregular
in form, and undergoes several divisions (Fig. 256, G).

The firat division in the embryo proper is almost vertical
(Fig. 256, F), and divides it into nearly equal parts. Beyond
this the early stages of the embryo were not followed by the
writer, but to judge from the later stages, they correspond to
those of 5. Martensiiy which has been most carefully studied
by Pfeffer,^ and the substance of which may be given as follows.
After the first wall is formed in the embryo, there arises in

» Pfeffer(i).

492

MOSSES AND FERNS

one of the cells a second, somewhat curved one, which strikes
the primary wall about half-way up. The cell thus cut off,
seen in longitudinal section, is triangular, and is the apical cell
of the stem (Fig. 257, A). The two other cells (leaf-
segments) now undergo division by a vertical wall, which
divides each into equal parts, and each of these pairs of cells
develops into a cotyledon. The apex of the young cotyledon
is occupied by a row of marginal celjs in which divisions are
formed, like those in the apical cell of the stem, and in longi-

A C

Coi

G ^ F.

Fig. 957. — SelagineUa Maritnsii (Spr.). Development of the embryo (after PfefferX A, B, D, E,
Successive stages in longitudinal section, X 3^0 ; C, apical view of a young embryo with four-sided
apical cell (jr), X 340 ; F, longitudinal section of the primary root, X 905 ; G, apex of the young
sporophyte, showing the first dichotomy, X 340.

tudinal section the apex of the cotyledon seems to have a
single apical cell, much like the stem (Fig. 257, E). From the
larger of the leaf- segments, by a more active growth of the
cells next the suspensor, the foot is formed, and by its growth
the stem apex is pushed to one side, and its axis becomes
almost at right angles to that of the suspensor. Elach
cotyledon develops upon its inner side, near the base, an
appendage, the ligula (Fig. 258, /), which is a constant
character of all the later leaves.

XIV

L YCOPODINE^

493

The primary root, as in Lycopodium^ forms late, and no trace
of it can be seen until the other parts are evident. It arises in
the larger leaf-segment, close to the suspensor, and therefore is
separated from the cotyledon by the foot. The root-cap arises
from a superficial cell, which divides early by both periclinal
and anticlinal walls, and thus becomes two-layered. From a
cell immediately below is derived the single apical cell to
which the subsequent growth of the root is due. The further
divisions in the primary root were not followed.

The axes of the stem and root soon develop a strand of
procambium which is con-
tinuous in the two, but to
judge from Pfeffer's figures,
the cotyledons do not de-
velop their vascular bundles
until later. The early
growth in length of the
root is mainly intercalary,
as the divisions in the
apical cell for some time
are not very rapid, and for
a long time the root-cap
consists only of the two
original layers.

With the growth of the
embryo the cell -formation
in the lower part of the
spore continues until it is
filled with a continuous
large-celled tissue, the con-
tents of whose cells are

much less granular than the undivided regions of the spore, and
as the embryo develops the foot crowds more and more upon
them until it nearly fills the spore-cavity.

On comparing PfefTer's account of 5. Martensii with my
own observations upon 5. Kraussiana, the main differences
consist first in the smaller development in the latter of the
primary prothallium, ue. the prothallial tissue formed before
the spores are shed, the archegonia being only separated from
the diaphragm by a single layer of cells instead of by three or
four, as in 5. Martensii. L, apus, which was also examined by

Fig. 258.— Longitudinal section of a fully-developed
prothallium aiS. Kranssiana^ with an advanced
embryo {tm\ X 77 ; /, ligula.

494

MOSSES AND FERNS

CHAP.

the writer, is intermediate in this respect between the two. A
second difference is the later period at which the cell division
in the lower part of the prothallium is completed in 5. Kraus-
siana. In this species, too, no root-hairs were seen, while
Pfeffer observed them in 5. Martensiu Finally, in the latter
the suspensor is much shorter and straighter than in 5.
Kraussiana,

In S, Martensii, almost as soon as the cotyledons are

Cot.

Fig. VLy^—SeUigitulla Kraussiana (A. Br.). A, Macrospore with the protballium (/rX X50; B,
young sporophyte still attached to the spore (*/), X 8 ; cot^ cotyledons ; R, root ; C, upper part of
an older stage, X 6 ; D, a still older one showing the first dichotomy, X 4

established, the two-sided apical cell of the stem is replaced
by a four-sided one, from which are then produced two similar
ones by the formation of a median wall, and a true dichotomy
of the primary axis thus takes place at once, the two new
branches growing out at right angles to the cotyledon. While
this may also occur in S. Kraussiana (Fig. 259, D), it is not
always the case, and frequently the young plant remains

LYCOPODINE^

495

unbranched until it has reached a length of a centimetre or
more, and has produced numerous leaves.

The Sporophyte

The sporophyte of Selaginella closely resembles that of
Lycopodium^ and, as in that genus, the leaves may be arranged
radially, or the stem may be dorsiventral with the leaves in
four rows ; the latter is much the commoner arrangement,
however, but 5. rupestris may be mentioned as a familiar
example of the homophyllous type. In many species there is

Fig. 260. — A, Part of a fruiting plant of Selaginella Kraussianay X 3 ; jr>, sporangial strobilus ; R,
young rhizophore ; B, longitudinal section of the strobilus, x 5 ; mta, macrosporangium ; m/,

microsporangium.

a creeping stem from which upright branches grow, much as
in many species of Lycopodium, but in others there is no clear
distinction between these parts. The roots may arise directly
from the ordinary branches, but in many species, e,g. S, Kraus-
sianay they are borne at the end of peculiar leafless branches
or rhizophores (Fig. 263, A). These, like the stem, show an
apparently regular dichotomous branching, which, however, is
really monopodial. The leaves, like those of Lycopodium, are
small, more or less lanceolate in outline, and with a single
median vein. In the dorsiventral shoots the leaves are

496 MOSSES AND FERNS chap.

arranged in four rows, two lateral ones, composed of large
leaves, and two dorsal rows of smaller ones (Fig. 260). In
the homophyllous forms the sporophylls differ but little in
appearance from the ordinary leaves, but in the heterophyllous
ones they are smaller than the other leaves, and always
arranged spirally about the axis, forming a strobilus much like
that of Lycopodium^ but usually less conspicuous. Commonly
the lowest or oldest sporangium is the macrosporangium, and
contains four spores ; the younger ones, which may continue to
form for a long time, are always microsporangia, and are very
similar in appearance to those of Lycopodium,

The Stem

The apex of the stem has the form of a cone, whose
summit, in most species examined, is occupied by a single
apical cell. This, in 5. Kraussiana (Fig. 261), is of the "tu'o-
sided " type, and segments are regularly cut off only from the
lateral faces. From inner cells of the segments are derived
the two vascular bundles (steles), which are found in the fully-
developed stem, but their limits are difficult to trace in the
small-celled meristem at the apex. In other species there is
great variation in the character of the apical meristem. Thus
in 5. Martensiiy according to Treub,^ the apical cell of the
older shoots may be either a two-sided one, like that of S,
Kraussiana, or it may be tetrahedral, like that of Equisetum
and most Ferns. In the younger branches, however, a four-
sided cell, like that Pfeffer describes for the embryo previous to
the first forking of the stem, is always present, but is later
replaced by the two-sided or tetrahedral form. Strasburger*
found in 5. Wallichii regularly two apical cells, and several
species, e,g. S, arborescens, 5. spinosa, show the same type of
apical growth as Lycopodium,

Sections of the stem apex, parallel to the plane of the
leaves, frequently show the formation of the branches (Fig. 261,
B). It is quite evident that the branch arises as a lateral out-
growth of the stem apex, which retains its original central
position for some time. The apical cell of the branch is not
established until the latter is very evident By the rapid
growth of the branch it may very early force the main axis
* Treub (i). ' Strasburger (7).

XIV

L YCOPODINE^

497

to one side, and thus produce the appearance of a true dicho-
tomy, but this does not always occur.

The leaves arise much in the same way that the branches
do, but do not develop a single apical cell. The growth is
much the same as in the first leaves of the embryo, and as in
these the early growth is due mainly to a row of marginal

Fig. ^1,—Selaginetla Kraussiana {\. Br.). Horizontal section of the apex of the stem, X77; B,
the apical meri^tem of the same, X450 ; x, the apex of the main axis ; x', a young lateral branch ;
B, B, young leaves ; L, ligula of the leaf ; C, D, longitudinal sections of the base of older leaves,
X 450 ; f , f , lacuna surrounding the vascular bundles of the stem ; /, one of the trabecular

initial cells from which segments are cut off alternately above
and below.

If we examine a longitudinal section of the stem a short
distance below the apex (Fig. 261, A), we find a regular
intercellular space formed between the central cylinder (or
cylinders), which completely surrounds it, and becomes very

2 K

498

MOSSES AND FERNS

conspicuous as the section is examined lower down. The
formation of this lacuna is similar to that in the capsule of the
Bryineae, and, as there, the central mass of tissue is connected
by rows of cells with the outer tissue. These rows of cells
(trabeculae) are at first composed of but a single cell, but later
by tangential walls become slender filaments by which the
vascular cylinders are suspended in

Fig. 262. — Cross-section of a fully-developed stem of S.
Kraussiatui, showing the two vascular bundles sus-
pended in the large central lacuna by means of the
trabecule (/), X 75 ; B, a single vascular bundle,
X 450 ; -r, jr, scalariform tracheids ; f, f , sieve-tubes.

the large lacuna which
occupies the centre of
the stem (Fig. 262, /).
According to Stras-
burger^ both the trabe-
culae, which are usually
regarded as endodermal,
and the pericycle, are of
cortical origin.

The fully -developed
bundle in 5. Kraussiana
(Fig. 262, B) shows a
pericycle composed of a
single layer of rather
large cells, within which
lies the phloem, which
completely surrounds the
xylem, as in the Ferns.
The sieve -tubes in this
species form a single
circle just inside the peri-
cycle, but according to
Gibson^ are absent op-
posite the protoxylem.
He states that there is
but a single group of
protoxylem elements
here, but my own ob-
that there are two, as Russow
origin of the protoxylem was

servations lead me to think

affirms is the case. The

not traced, but the appearance of the mature bundle in the

specimens examined (Fig. 263, B) points to this conclusion.

The protoxylem is made up of small spiral and annular

tracheids, the metaxylem (secondary wood) of larger scalari-

^ Strasburger (7), p. 457. * Gibson (2), p. 176.

LYCOPODINEJ£

499

form elements, as in Lycopodium, The sieve-tubes have delicate
walls and numerous, but poorly developed, sieve -plates upon
their lateral walls.

While in the main the anatomical characters are essentially
the same in all species examined, there are a number of
differences to be noted.^ ' Thus the stem may be monostelic
(5. Martensit), bistelic (5. Kraussiana)^ polystelic (5. Ic^i-
gatd). In the former species the presence of silica in the
inner cortex has been ' demonstrated by Strasburger, and
Gibson ^ has shown the same thing in other species. In this
species, too, besides the simple trabeculae found in 5. Kraussiana^

Fig. 263.— a, Rhizophore, with roots of .S'. Kraussiana, X i J ; B, cross-section of the vascular
bundle of a root, X430 ; C, median longitudinal section of the Jeaf, X2i5.

Others occur in which the outer cells undergo divisions in more
than one plane, and form a group of cells with which the
endodermial cell is articulated. In all species examined these
cells show more or less marked cutinisation. The number of
protoxylems in most species is two, but there may be accessory
ones.

The cortex is composed in most species of delicate paren-
chyma, with few or no intercellular spaces, and most of the
cells contain chlorophyll. In species like 5. lepidophylla, which
grow in dry localities, the cortical cells are sclerenchymatous,

* Gibson (2), p. 176.

« Gibson (I).

50O MOSSES AND FERNS chap.

with deeply-pitted walls. In the creeping stems, even in poly-
stelic species, there is but a single stele, which gradually passes
over into the separate steles of the upright stems.

The leaves show a single very simple concentric bundle,
similar to those of the stem, but less developed. The leaf-
traces, as in Lycopodiunty join the * central vascular cylinder
(Fig. 261, C). The leaf always develops a ligula just above
the base. This (Fig. 261, L) is a tongue-shaped organ, which
cannot be traced back to a single cell. The basal cells are
larger than the others, and it is much constricted at the point
where it joins the leaf.

T/ie Roots

The roots in 5. Kraussiana are borne upon the special
leafless branches or rhizophores, which in structure are much
like the stem. Previous to the formation of the first roots
upon the rhizophore,^ the apical cell is obliterated and replaced
by a group of initial cells. The apical cells of the (usually
two) roots formed arise secondarily, and quite independently
of each other, from cells lying below the surface, and covered
with one or two layers of cells. These cells soon assume a
tetrahedral form, and become the apical cells of the primary-
roots. The branching of the roots, like that of the stem, is
really monopodial, although apparently a true dichotomy.

The vascular bundle of the root is monarch (Fig. 263, B),
and does not show a distinct endodermis. The phloem sur-
rounds the xylem completely, but apparently sieve -tubes are
not developed opposite the protoxylem. The elements of the
bundle are in structure like those of the stem-bundles.

Tlie Chloroplasts

The chloroplasts of Selaginella are peculiar, on account of
their large size and small numbers. A careful study has been
made of these by Haberlandt,^ who found that in each of the
meristematic cells of the stem apex a single plastid was
present. This in the assimilative cells of the leaves either
remains undivided (5. Martensit)^ or it may become more or less
completely divided into two (5. Kraussiana), In 5. Willdenowii

1 Sadebeck (6). « Haberlandt (9).

L YCOPODINE^

501

there may be as many as eight In the cortical parenchyma
of the stem the chloroplasts are apparently of the ordinary
form, but a careful examination shows that they are all con-
nected, and are directly referable to the divisions of the primary
plastid in the young cell. In all cases the nucleus is in
contact with the chloroplast or group of chloroplasts (Fig. 264).
The character of the chloroplasts here has its nearest analogy
in Anthoceros, where occasionally a division of the chloroplasts

n..— w

FiG. 264.— A, B, Cells of the mesophyll of Stlaginella Mariensii^ showing the single chloroplast (<"/)
and the nucleus (k) ; C, chain of connected oval chloroplasts from the inner cortex of the stem of
S. Kraussiana, X 64c (after Haberlandt).

is met with, especially in the elongated cells of the sporo-
gonium.

The Sporangia

The development of the sporangia is much like that of
Lycopodiumy and has been studied by Goebel ^ and Bower in
S, spinosa, and by the latter in 5. Martensii also. In 5.

J Goebel (16), p. 388 ; Bower (15).

502

MOSSES AND FERNS

Kraussiana (Fig. 265, A) a radial section of the young
sporangium shows a very regular arrangement of the cells, with
a single central archesporial cell (the nucleated cell of the
figure). This evidently has arisen from a hypodermal cell of
the central row, and from it is already cut off by a periclinal,
an outer cell. The whole closely resembles Goebel's figures
of 5. spinosa, A comparison with older stages indicates that
from this central cell alone the sporogenous cells are produced,
as in Lycopodium selago. The outer row of cells does not
divide by periclinal walls, and from the first forms an extremely

Fig. 265. — Seiag^tuiia Kraussiana (A. Br.). Development of the microsporangium, radial sections.
A-C, X SCO ; D, X 235. The nuclei of the archesporial cells are shown. L, The leaf subtending
the sporangium.

distinct layer. The first cell cut off from the archesporium
divides again by a periclinal wall (Fig. 265, B), and the inner
cell forms probably the first tapetal cell, although in some
cases it looks as if this cell took part in the formation of
spores. The archesporium undergoes repeated divisions to
form the sporogenous tissue, and finally the layer of cells
between these and the primary wall divides by periclinal walls
to form the tapetum, which here remains intact until the spores
are nearly or quite mature. The formation of the stalk is
the same as in Lycopodium,

L YCOPODINE^

503

Bower ^ thinks it probable that in 5. spinosa and 5.
Martensii the sporogenous tissue cannot be traced back
always to a single cell (in radial section), and has also shown
that when tangential sections are examined, as in Lyco-
podium^ the archesporium always is a row of cells.

In all species of Selaginella yet examined, the sporangium
is not of foliar origin, but originates from the axis above the
insertion of the leaf by which it is subtended.

As in Lycopodium the tapetal cells do not become dis-

Fic, 266. — Selaginella Kraussiana (A. Br.). A, Radial section of a nearly ripe microsporangiuin,
X 100 ; /, ligula of the subtending leaf ; /, tapetum ; B, section of young macrosporangium (about
half grown), showing the papillate tapetal cells (/), X 600 ; C, section of the wall of a young
macrospore from the same sporangium, X 600.

organised, but remain intact as the inner layer of cells of the
three-layered sporangium wall. They form an epithelium-like
layer of papillate cells, distinguished by their dense granular
contents, and it is evident that they are actively concerned in
the elaboration of nutriment for the growth of the young spores
(Fig. 266).

As in the other heterosporous Pteridophytes, the two sorts
of sporangia are alike in their earlier stages, and this in Sela-

1 Bower (15), pp. 523, 524.

504 MOSSES AND FERNS chap.

ginella continues up to the time of the final division of the spore
mother cells, each of which divides into four tetrahedral spores.
These in the microsporangium all develop, but in the macro-
sporangium only one of the tetrads reaches maturity. The
tetrad of macrospores fills the sporangium completely, and
with their growth the sporangium itself becomes four-lobed,
and very much larger than the microsporangia. The cells of
the wall remain green and fresh up to the time that the
macrospores are ripe, and sections show that the tapetal cells
are in close contact with the wall of the spores. The episporic
ridges are very evident before the spore has reached half its
final diameter, and sections of the spore wall at this time (Fig.
266, C) show the spine-like section of the surface ridges. The
wall rapidly increases in thickness as the spores grow, and this
increase is evidently due almost entirely to the activity of the
tapetal cells, as the spore at this stage contains very little
protoplasm. The first nuclear division in the macrospore
takes place when the spore is about half-grown, and by the
time it has reached its full size the cell divisions in the apical
region are complete and the archegonia have begun to form.

The ripe sporangium, as in Lycopodium^ opens by a
vertical slit.

The Affinities of the Lycopodinece

Among the living Lycopodineae there are two well-marked
series, one inckiding the Lycopodiaceae and . Selaginelleae, the
other the Psilotaceae. In the first, beginning with Phyllo-
glossum^ the series is continued through the different forms
of Lycopodium to the Selaginelleae. The relation of the
Psilotaceae to this series is doubtful, and must remain so until
the sexual generation of the former is known. The probable
saprophytic or parasitic life of these plants makes it impossible
to determine just how far their simple structure is a primitive
character rather than a case of degradation.

Of the first series, it seems probable that of the forms
whose life history is known, the type of L, cemuum represents
the most primitive form of the gametophyte. It is reasonable
to suppose that in all these forms the prothallium was green,
and that the saprophytic prothallia, like those of Z. phlegntaria
and Z. annoiinuffiy are of secondary origin. The prothallium, •
of the type of L, cemuum^ may be directly connected with

LYCOPODINE^ 505

Liverworts like AnthoceroSy and resembles them also in the
small biciliate spermatozoids, in which latter respect all the
Lycopodineae yet examined agree. This latter point is per-
haps the strongest reason for assuming that the Lycopods
represent a distinct line of development, derived directly from
the Bryophytes, and not immediately related to either of the
other series of Pteridophytes. The character of the arche-
gonium, as well as the long dependence of the embryo upon
the prothallium and the late appearance of the primary root,
point to the genus Lycopodium as a very primitive type, even
more closely related to the Bryophytes than are the eusporangi-
ate Ferns. Phylloglossum, at least so far as the sporophyte is
concerned, is the simplest living Pteridophyte ; whether the
structure of the gametophyte will bear this out, future investi-
gation must determine.

The close relation of Selaginella to Lycopodium is sufficiently
obvious. It is, however, interesting to note that Selaginella
seems to have retained certain characters that are apparently
primitive. These are the presence of a definite apical cell in
the stem and root of most species, and the peculiar chloroplasts,
which are especially interesting as a possible survival of the
type found in so many Confervaceae, e,g. ColeocJicete^ from which
it is quite likely that the whole archegoniate series has
descended. This form of chloroplast occurs elsewhere among
the Archegoniatae only in the Anthoceroteae.

In the characters of the sporangium and the early develop-
ment of the prothallium, Selaginella undoubtedly shows the
closest affinity to the Spermaphytes, especially the Gymno-
sperms, of any Pteridophyte. The strobiloid arrangement of
the sporophylls and the position of the sporangia are directly
comparable to the strobilus of the Coniferae. The wall of the
sporangium is here not only morphologically, but physiologic-
ally comparable to the nucellus of the ovule, and, as there, the
macrospore grows^ not at the expense of the disorganised
sporogenous cells and tapetum alone, but is nourished directly
from the sporophyte through the agency of the cells of the
sporangium stalk and wall, until the development of the
enclosed prothallium is far advanced. The latter, both in its
development while still within the sporangium, as well as in
all the details of its formation, shows the closest resemblance to
the corresponding stages in the Conifers. The formation of a

5o6 MOSSES AND FERNS chap.

"primary" and "secondary" prothallium is, as we have seen,
only apparent, and the diaphragm in the prothallium of
Selaginella is not a true cell wall, marking a primary division
of the spore contents, but only a secondary thickening of the
lower walls of certain cells, indicating a temporary cessation in
the process of cell-formation. It is by no means improbable
that this cell-formation, may sometimes go on uninterruptedly,
in which case no diaphragm would be formed, and, as in Isoetes^
there would be no distinct line of demarcation between the
archegonial tissue at the apex and the large-celled nutritive
tissue below.

The presence of a suspensor in all investigated Lycopodineae
is a character which distinguishes them at once from the other
Pteridophytes, and has its closest analogy again among the
Conifers.

Fossil Lycopodinece ^

Many fossil remains of plants undoubtedly belonging to
the Lycopodineae are met with, especially in the Coal-measures,
where the Lepidodendreae were especially well developed. Of
homosporous forms, it seems pretty certain that the fossils
described under the name Lycopodites are related to the living
genus Lycopodium^ and certain fossils from the Coal-measures
have even been referred to the latter genus, some of these
being homophyllous, others heterophyllous. Solms-Laubach
thinks it somewhat doubtful whether the plants described by
various writers, and belonging to older formations, really are
Lycopodineae.

In regard to the Psilotaceae he says : " The statements
respecting fossil remains of the family Psilotacece are few and
uncertain, nor is this surprising in such simple and slightly
differentiated forms. If Psilotites . . . does really belong to
this group, a point which I am unable to determine from the
figures, we should be able to follow the type as far down as
the period of the Coal-measures."

The genus Psilophyton, which has been found as far back
as the Upper Silurian, is regarded by Dawson ^ as related to the
Psilotaceae, but there seems some question about the accuracy
of his conclusions.

The well-known group of the Lepidodendrese is one of the

^ Solms-Laubach (2). ' Solms-Laubach (i), p. 19a

LYCOPODINEJi 507

most characteristic ones of the Coal-measures, where their
remains occur in enormous quantities. While evidently related
to the modern Lycopodineae, they were different in some
respects, especially the gigantic size of some species, which
reached tree-like proportions. The leaves were deciduous,
and in falling off left the characteristic rhombic leaf-cushions
exposed. The structure of the stem^ is not unlike that of
LycopodiufHy and shows a central bundle-strand surrounded by
a massive cortex, through which pass the leaf-traces. In some
cases the increase in thickness of the stem was due mainly to
the cortex, but specimens have been found in which there was
an undoubted secondary thickening of the vascular bundles,
quite similar to those in Gymnosperms.

The sporangia have been preserved with wonderful perfec-
tion in a few cases, and their structure is well known.*^ In
position they correspond to those of Lycopodiunt^ but were
heterosporous, somewhat like Selaginellay but usually the
macrospores were much more numerous. These sporangia!
strobili of Lepidodendron were first described under the name
Lepidostrobus, Bower,* who has recently carefully examined
their structure, states that the cavity of the large sporangium is
divided by incomplete trabeculae, somewhat as in Isoetes.

Probably rela'ted to the Lepidodendreae are other large
lycopodinous forms occurring in the same geological formations,
and grouped together under the name Sigillarieae. They show
similar markings upon the surface of the stems, but their struc-
ture and fructification are much less perfectly known than is
the case with the Lepidodendreae, with which, however, they
seem to agree in the main.

The genus Stigniaria has been conclusively shown to
be nothing but the roots or rhizomes of Lepidodendreae or
Sigillarieae.

The Lepidodendreae have been traced as far back as the
Lower Devonian,^ but the Sigillarieae are not known certainly
below the Coal-measures, and both groups disappear before the
end of the Carboniferous period.

' Solms-Laubach (i), p. 215. ^ Bower (15).

' Bower, l.c. p. 527. "• Solms-Laubach (2), p. 194.

CHAPTER XV

SUMMARY AND CONCLUSIONS

The Interrelationships of the ArcJugoniatcB

It is pretty generally conceded that the origin of the whole
archegoniate series is to be sought somewhere among the green
Algae, and that on the whole Coleoclicete is, perhaps, the fomri
which is nearest to the simplest Muscineae. While the
Characeae, as we have seen, approach the latter more nearly
in the structure of the sexual organs, yet the character of the
vegetative parts is so different from that of any of the Muscineae,
and the sporophyte is so simple, that any close relationship of
the two groups is hardly probable. At best, the connection
between any known Alga and the Muscineae is a very remote
one.

From a study of the facts presented in the foregoing pages,
the conclusion has been reached that the Hepaticae are not only
the most primitive of the existing Archegoniatae, but are also
the forms from which all the other groups have descended.
When, however, the question arises as to which of the existing
groups of Liverworts is the most primitive, the matter is not so
easy to settle. Thus while Riccia undoubtedly has the most
primitive sporophyte, the gametophyte shows a much higher
degree of differentiation than is found in most anacrogynous
Jungermanniaceae and the Anthoceroteae. The latter group,
while retaining an extremely simple type of gametophyte, has
the sporophyte developed beyond that of any other Bryophyte.
It will be remembered that in the germination of most
^ tballoid Liverworts (and occasionally in the foliose forms as
,N*#ell) the occurrence of a single two-sided apical cell is quite
general, although this may be absent from the fully-developed

CHAP. XV SUMMARY AND CONCLUSIONS 509

gametophyte. This suggests the possibility of a derivation of
all of them from some type in which this two-sided apical cell
was permanent. Aneura and Metzgeria^ among living genera,
have retained this condition, and in this respect are possibly
to be considered as representing the simplest type of the thallus.
The peculiar gemmae of the former, which may properly be
compared to the zoospores of Coleocliaie^ strengthen this view.

Starting from this primitive type, we have endeavoured
to show that development proceeded along three lines — the
Marchantiaceae, the Jungermanniaceae, and the Anthoceroteae.
In the first one the differentiation consists mainly in the
specialisation of the tissues, while the gametophyte retains its
strictly thallose character ; in the Jungermanniaceae it is rather
in the direction of the development of appendicular organs,
while the tissues remain nearly uniform. In both of these
groups the sporogonium is comparatively simple, in strong
contrast to the Anthoceroteae. Whether the peculiar chloro-
plasts of the latter are of secondary origin, or have been
inherited directly from ancestors like Coleocliate, where the same
form occurs, it is not possible to determine. The great prepon-
derance of the foHose Liverworts indicates that they are com-
paratively modern types, which have adapted themselves to
present conditions, and show no indications of being connected
directly with any higher forms.

Just as the simplest Jungermanniaceae may have served as
a starting-point for the three main lines of development in the
Liverworts, so the Anthoceroteae show evidences of being the
ancestors of two other lines, the Mosses and the Pteridophytes.
Whether the former class constitutes a continuous series, begin-
ning with Sphagnum, or whether the Sphagnaceae and the
higher Mosses represent two branches from a common stock,
it seems extremely likely that the thalloid protonema is the
primitive condition derived from some Liverwort-like form allied
to Anthoceros, and that the alga-like protonema of the higher
Mosses is a secondary development from it.

In tracing the gradual evolution of the sporophyte among
the Muscineae we have seen how, starting with the simple
sporogonium of Riccia, which, physiologically, is only a spore-
fruit and quite incapable of independent growth, it gradually
becomes more and more independent by the development of a
special system of assimilative tissues, which reaches its extreme

510 MOSSES AND FERNS chap.

in Ant/ioceros, It is true that the sporogonium always remains
to some extent parasitic upon the gametophyte, but this
parasitism is very slight in Anthoceros^ where the formation of a
root would make the sporogonium quite self-supporting. This
increase in the vegetative tissues of the sporophyte is at the
expense of the sporogenous tissue, which becomes more and
more subordinated to the assimilative and conductive tissue of
the sporogonium, as is seen in the Bryineae among the Mosses,
and in Antftoceros.

In most of the Liverworts the sterile tissues of the sporo-
gonium are mainly concerned with the protection and dissemin-
ation of the spores. Only the foot, usually, can be properly
considered as an organ concerned in the nourishment of the
growing embryo. The seta, capsule wall, and elaters are
merely adaptations for facilitating the dispersal of the ripe
spores. In all of these, except the Anthoceroteae, the whole of
the central tissue of the capsule constitutes the archesporium,
all of whose cells are devoted to the formation of spores or
elaters. In the Anthoceroteae, however, the origin of the arche-
sporium is quite different, and it arises not from the central cells,
but by a secondary division of the parietal ones. As yet there
is no clear evidence of a direct connection with either of the
other series of the Hepaticae, and it is a question whether the
Anthoceroteae ought not to form a group co-ordinate with all
the other Liverworts on the one hand, and the Mosses on the
other. It is possible that the axial bundle of sterile cells found
in the capsule of Pellia and Aneura may be homologous with
the columella of the Anthoceroteae, and the latter therefore to
be considered as derived directly from some simple form among
the anacrogynous Jungermanniaceae ; but as the sporogonium
in all the Anthoceroteae that have been thoroughly investigated
shows absolutely the same type of structure, and in no case a
secondary formation of the columella, this is hardly probable.
In the higher Anthoceroteae, also, the wall of the capsule,
instead of simply serving for the protection of the spores,
becomes a massive spongy green tissue communicating with
the atmosphere by means of perfectly -developed stomata of
exactly the same type as those of the vascular plants. This
similarity in the assimilative system, together with the basal
growth of the sporophyte and the central strand of conductive
tissue, has of course suggested a relationship with the vascular

XV 5 UMMAR Y AND CONCL USIONS 5 1 1

plants. Indeed the sporogonium of Anthoceros is much more
like a small Ophioglossum, for example, than it is like the
sporogonium of Riccia,

The Mosses, like the foliose Liverworts, seem to represent
a modern, extremely specialised type, with no direct connection
with higher forms. Undoubtedly related to the Anthoceroteae
through Spliagnum^ their further development has diverged
farther and farther away from the other Archegoniatae, until in
the Bryineae both gametophyte and sporophyte have little in
common with them.

The three classes of the Pteridophytes, while they differ
strongly in the form of the sporophyte, are yet so much alike
in the essential characters of the sexual generation, as to make
it inconceivable that they can have originated from very widely
separated ancestors. The more closely the gametophyte is
studied in all of them, the more evident becomes the strong
resemblance to the Anthoceroteae, whose sporogonium has
always been recognised as the nearest approach to the
sporophyte of the vascular Archegoniates. This is notably
the case when we consider the structure and development of
the sexual organs, which in the Anthoceroteae differ so re-
markably from those of the other Muscineae. Whether the
submersion of the archegonia and antheridia in the thallus is
the result of the cohesion of an envelope, such as is formed
about these in Spfuerocarpus or Riccia^ it is impossible to
say, as there is no trace of any such process in the develop-
ment of the sexual organs in any of the investigated
species.

The probable homology of the four -rowed neck of the
archegonium of the Pteridophytes with the cover cells only of
the Liverwort archegonium, has already been discussed at length
in a preceding chapter. It is quite possible that a similar
correspondence may exist between the antheridium in the
lower Pteridophytes and the Anthoceroteae. It will be re-
membered that in the latter the single antheridium, or group
of antheridia, arises from the inner of two cells formed from
the division of a superficial cell of the thallus, and that the
inner cell may either give rise to a single antheridium, or more
commonly, by repeated longitudinal divisions, a group of
antheridial mother cells is formed. The whole process is
strikingly different from the development of the superficial

512 MOSSES AND FERNS chap.

antheridia in the other groups of Liverworts. In all of the
homosporous Pteridophytes except the leptosporangiate Ferns,
however, the first division in the antheridial cell is exactly as
in the Anthoceroteae ; but instead of the inner cell developing
into a distinct antheridium, the whole of it is devoted to the
formation of sperm cells. It seems not improbable that this
type of antheridium may have been derived from that of the
Anthoceroteae by the suppression of the parietal cells of the
antheridium.

Aside from the forms without chlorophyll, which are
probably all secondary, the Pteridophytes show three types of
gametophyte. The first, represented by most homosporous
Ferns, is the familiar heart-shaped prothallium, which strongly
recalls the simpler anacrogynous Jungermanniaceae or Dendro-
ceros ; the second is the lobed prothallium of Equisetum and
Lycopodium cemuunty which resembles most nearly among the
Hepaticae such forms as Anthoceros fusiformis ; finally, in
some species of Trichomanes there occur the branched fila-
mentous prothallia, which some authors look upon as an
indication of direct relationship with forms intermediate
between Algae and Muscineae. As other species have the
same type of prothallium as the other Ferns, and this is always
true of the closely related genus Hytnenophyllum^ this view is
open to question.

As far as the form and growth of the prothallium are con-
cerned, all forms could be traced back to the Anthoceroteae ;
the Fern type to forms like Dendroceros or Anthoceros kevis^
the Equisetum and Lycopodium type more resembling A.
fusiformis. The difference in the character of the chroma-
tophores is a very important one, and at present must forbid
the assumption of any immediate connection between the
Anthoceroteae and existing Pteridophytes. Whether the occa-
sional appearance of very large plate-like chromatophores in
the prothallium of Osmunda cinnamomea is a reversion to a
primitive condition retained in the Anthoceroteae, it is, of course,
impossible to say, but it is not inconceivable, especially as
the same thing is found again normally in the sporophyte
of Selaginella,

In the Anthoceroteae the origin of the archesporium is
different from that of the other Hepaticae, being hypodermal>
as in the lower Pteridophytes. The columella is in position

XV SUMMARY AND CONCLUSIONS 513

similar to the primary vascular bundles in the embryo of
the Pteridophytes, and in all probability is to be regarded
as its homologue. This central strand of conducting tissue,
together with the massive assimilative tissue system of the
larger species of Anthoceros^ would make the sporogonium
independent of the gametophyte, were a root or some similar
structure present by which it could be connected with the
earth. The alternation of sporogenous and sterile cells in the
archesporium, by which the latter is divided into imperfect
chambers containing the spores, is, perhaps, the first indication
of the separate sporangia of the Pteridophytes. The most
striking difference, then, between the sporogonium of Anthoceros
and the sporophyte of the simpler Pteridophytes, such as
Ophioglossutn and Phylloglossum^ aside from the absence of
roots, which are, physiologically, replaced by the massive foot,
is the absence of a definite axis with its lateral appendages
(leaves) and sporangia. In Anthoceros the assimilative tissue
forms a uniform layer over the whole upper portion of the
sporophyte, instead of being restricted mainly to the special
organs of assimilation or leaves, and the archesporium is
continuous instead of being divided into definite sporangia.

Many attempts have been made to explain the origin of
the leafy axis of the sporophyte of the vascular Archegoniates
from the Bryophyte sporogonium. The latest theory is that
of Professor Bower,^ who has brought forward much important
evidence to show that the simpler strobiloid Pteridophytes,
especially Phylloglossum^ are the primitive forms from which
the others have sprung. His conclusions are based largely
upon a comparison of Phylloglossum with the embryonic con-
dition of Lycopodium^ where the long dependence of the
embryo upon the prothallium, the rudimentary vascular
bundles, and the late appearance of the root are very striking,
and certainly indicate a very low rank for these forms in the
pteridophytic series. Another evidence of the close relation
of the Lycopodineae to the Bryophytes is the character of the
spermatozoids, which closely resemble those of the Liverworts,
both in their small size and the two cilia. Professor Bower's
theory as to the origin of the sporophytes is that these arose
" by a process of eruption from a hitherto smooth surface."
In this way he conceives that the smooth cylindrical sporo-

* Bower (16).
2 L

5*4 MOSSES AND FERNS chap.

gonium became transformed into a structure directly comparable
to the strobilus of Phylloglossum. The sterile leaves, as well
as the root, are supposed to be outgrowths of the proto-
corm, which latter is directly comparable to the massive foot in
AnthoceroSy whose upper limit is the meristematic zone of cells
at the base of the capsule. Bower summarises his conclusions
as follows : ^ " The chief points which have been recognised thus
far, and are believed to have been the important factors in
advance, are: (i) sterilisation of potential sporogenous tissue;
(2) formation of septa ; (3) relegation of the spore -producing
cells to a superficial position; and (4) eruption of outgrowths
(sporangiophores) on which the sporangia are supported."

Professor Bower's explanation of the origin of the Lyco-
podineae is certainly the most satisfactory that has yet been
given, and we may accept without much question his conclusion,
that Phylloglossum is on the whole the simplest known Pterido-
phyte ; but his further conclusion that the Ferns are also prob-
ably reducible to a strobiloid type is by no means convincing.

The conclusion reached by the author, after considerable
study of the subject, is that in the Ferns, and probably also the
Equisetineas, we have to deal with entirely distinct lines of
development. That is, while all three groups of the existing
Pteridophytes may be traced back to a common stock, closely
allied to the Anthoceroteae, the three lines became differentiated
at a very early period, and the differences are so great that it
is difficult to see how any one of them could have been derived
directly from either of the others. In the Lycopodineae and
Equisetineae the axis is developed much more strongly than the
leaves, and the sporophylls are usually aggregated into a more
or less definite strobilus. The origin of the strobilus in the
Equisetineae may have been similar to that in Lycopodium ;
but the sporangia themselves, as well as the structure of the
tissues and the prothallium, are more like those of the Ferns,
and make it extremely improbable that the strobilus is homo-
logous with that of the Lycopodineae. In the very definite
apical growth of the stem and root, as well as in the structure
and arrangement of the vascular bundles, Equisetum approaches
much more nearly the condition found in Ophtoglossum than
that of the Lycopodineae ; and the large multiciliate spermato-
zoids, and the early divisions of the embryo, are also suggestive
' Bower (16), p. 360.

XV SUMMARY AND CONCL USIONS 5 1 5

of the Ferns rather than of the Lycopods. Of course the fact
that our knowledge of the Equisetineae is mainly based upon
the single genus Equisetum, makes it unsafe to lay too much
stress upon conclusions drawn from a study of this single type.
However, such of the fossil forms as show unmistakable evidence
of belonging to the Equisetineae, conform closely in their
structure, so far as it is known, to the living types.

In the Filicineae the development of the leaves is usually
much greater than in either of the other classes, and the origin
of the sporophyll is probably different. Bower considers the
sporophyll of Ophioglossum, for example, as the homologue of
a single sporophyll of Lycopodium, and the whole sporangial
spike as equivalent to a single sporangium. With this view the
author feels that he cannot agree, and it seems more likely that
the origin of the Fern-type of sporophyte was quite different
from that of the Lycopodineae, and that there is nothing among
the Ferns comparable to the strobilus of the latter.

If we could imagine the meristem at the base of the
sporogonium of Anthoceros to produce a lateral flattened
appendage or leaf, and the foot to develop into a root penetrat-
ing the thallus into the earth, we should have a structure not
very unlike a small Opkioglossum, In this case the sporangial
spike would represent, not a single sporangium of Phylloglossum^
but the whole strobilus, and the sterile segment of the leaf
would then be comparable rather to the sterile leaves (proto-
phylls) than to a single sporophyll.

While the Lycopodineae correspond closely to the Bryo-
phytes in the form of the spermatozoids, these in the other
Pteridophytes are large and multiciliate. Whether these
peculiarities have arisen independently in the Filicineae and
Equisetineae, or whether they are inherited from some common
ancestor, there is no means of deciding. None of the Muscineae,
so far as is known, depart from the biciliate type, but among
Algae, CEdogonium offers a similar exception to the usual
biciliate form.

The Lycopodiaceae and Selaginelleae constitute a sufficiently
direct series, but the exact affinity of the Psilotaceae to these is
by no means clear. Our complete ignorance of the sexual
stage of tlie latter, as well as their parasitic habit, makes it
impossible to judge just how far their simple structure is
primary and how much is due to reduction.

5i6 MOSSES AND FERNS chap.

The reasons for regarding the eusporangiate Ferns as the
lowest of the Filicineae have been already given at length,
but may be summarised as follows: (i) The structure of the
gametophyte and sexual organs corresponds more nearly to
^that of the Liverworts than do those of the Leptosporangiatas,
and the prothallium is larger and longer lived than in
the latter ; (2) the embryo remains much longer dependent
upon the gametophyte, and the latter may live for a long time
after the sporophyte becomes independent ; (3) the differenti-
ation of the organs and tissues of the embryo takes place
later than in the Leptosporangiates, and the tissues of the
mature sporophyte are also simpler than in most of the latter ;
(4) the sporangia of the Eusporangiatae, especially Ophto-
glossunty are of a much less specialised type than in the
typical leptosporangiate Ferns, and approximate more nearly
the condition found in Anthoceros ; (5) the small number of
species of the Eusporangiatae, but the wide divergence of type
shown, especially by the two groups of the Ophioglossaceae and
Marattiaceae, indicate that these are remnants of formerly more
predominant forms. Finally, the strong evidence of the
geological record that the Eusporangiatae were the prevailing
types in the earlier formations, and have been supplanted by
the more specialised Leptosporangiatae in more recent times,
is reasonably conclusive.

The homosporous Leptosporangiatae constitute a pretty
continuous series, beginning with the Osmundaceae, by which
they join directly to the Eusporangiatae, and ending with
the Polypodiaceae. From this stock the two heterosporous
families, the Marsiliaceae and Salviniaceae, have branched off
independently of one another.

The systematic position of Isoetes is very difficult to settle,
but on the whole its affinities appear to be with the lower
Eusporangiatae.

The development of heterospory in the different groups
of the Pteridophytes is of especial interest, from its bearing
upon the question of the origin of the Spermaphytes. That
heterospory arose in a number of widely remote groups is
unquestionable. While among the living Pteridophytes it is
confined to the Ferns and Lycopods, the very perfect fossil
remains of Calamostdchys show that heterospory was also
developed in the Equisetineae, although apparently the differ-

XV SUMMARY AND CONCLUSIONS 517

ence between the two sorts of spores was less marked than
obtains in the other two classes. In the leptosporangiate
families, the Marsiliaceae and Salviniaceae, although there is
great reduction in the size of the prothallium, its development
is essentially the same as in their homosporous relatives, and
the female prothallium, if unfertilised, usually develops chloro-
phyll, and is capable of independent growth ; but in the
Isoetaceae and Selaginelleae the formation of the female pro-
thallium is much more like that in the Spermaphytes, and
makes it extremely likely that from some such forms the
latter have been derived.

The microsporangia of the Spermaphytes do not differ
essentially from those of the heterosporous Pteridophytes, and
the microspores (pollen spores) are shed before germination.
The macrospore (embryo-sac), however, is retained within the
macrosporangium (ovule), where it remains during the whole
period of germination. Among the Pteridophytes Selaginella
approaches this condition, as the macrospore is retained within
the sporangium until germination is far advanced. The integu-
ment of the ovule is, with very little question, homologous
with the indusium. The young macrosporangium of Azolla is
extraordinarily like a developing ovule, and the closely invest-
ing indusium has all the appearance of an ovular integument.
The velum of Isoetes is possibly of the same nature.

The development of heterospory in several unrelated groups
of Pteridophytes at once suggests the possibility of a multiple
origin for the Spermaphytes. The radical differences between
Gymnosperms and Angiosperms, and the absence of any truly .
intermediate forms, make it extremely probable that these two
great divisions have originated independently of one another, prob-
ably from different stocks, and it is by no means unlikely that
the same may be said of the Cycads, Conifers, and Gnetaceae.

Except for their siphonogamic fertilisation, the Gymno-
sperms really are much nearer the Pteridophytes than they are
to the Angiosperms. As both the pollen tube and the seed-
formation are but further developments of heterospory, it is
quite conceivable that these might have arisen independently
more than once. The close resemblance between the Conifers
and the Lycopods, especially Selaginella^ probably points to a
real relationship. The strobiloid arrangement of the sporo-
phylls, as well as the development of the prothallium and

5i8 MOSSES AND FERNS chap.

embryo, are extraordinarily similar, and it is not unreasonable
to suppose that this is something more than accidental.
Whether the Cycads belong to the same stock, or, as has been
frequently suggested, are more nearly allied to the Filicineae,
further investigation must decide.

The Angiosperms are in all probability all members of a
common developmental series, bi^t just what is their relation
to one another and to the other vascular plants is not so
evident. It is usually held that they have been derived from
the Gymnosperms through the Gnetaceae, but it has also
been suggested that one or both of the divisions may have
originated directly from the Pteridophytes. Attention has
been called more than once to the close resemblance between
the embryos of the Filicineae and those of typical Monocoty-
ledons, and this is especially the case in Isoetes^ where, in
addition, the structure of the mature sporophyte is much like
that of the Monocotyledons. It is possible that the surround-
ing of the sporangium by the base of the sporophyll may be
the first indication of the ovary of the Angiosperms, but as
this applies to the microsporangia as well, much stress cannot
be laid upon it. It is quite as easy to trace back the embryo-
sac of the Angiosperms to the macrospore of Isoetes as to the
embryo-sac of the Gymnosperms ; and when the great similarity
between the sporophyte of the former and the Monocotyledons
is considered, the probability of the origin of the lattqr from
aquatic or semi-aquatic ancestors resembling Isoetes is certainly
considerable.

The essential similarity in the structure of the embryo-sac
in all Angiosperms yet examined (except Casuarind)y as well
as the structure of the flower, makes it almost inconceivable
that the two branches, Monocotyledons and Dicotyledons, could
have arisen from different stocks. Strasburger's suggestion
that the Dicotyledons were derived directly from the Gymno-
sperms, and that the Monocotyledons are a reduced branch of
the former, is open to objections both on morphological and
palaeontological grounds, and we believe that the evidence we
have at present points to the Monocotyledons as the more
primitive of the two divisions of the Angiosperms, from which
later the Dicotyledons branched off. If, as we have assumed,
Isoetes has its affinities with the lower eusporang^ate Ferns,
the Angiosperms would be connected directly with them

SUMMARY AND CONCLUSIONS

519

through Isoetes, and the Eusporangiatae would bear somewhat
the same relation to the Angiosperms and Leptosporangiatae
that the Anthoceroteae do to the Musci on the one hand, and
the Pteridophytes on the other.

To summarise briefly : the conclusion reached is that the
Spermaphytes represent not one single line of development,
but at least two, and perhaps more, entirely independent ones,
having their origin from widely separated stocks. The Gymno-
sperms (at least the Conifers) are probably direct descendants
of some group of Lycopods allied to the Selaginelleae, while
the origin of the Angiosperms is to be looked for among the
eusporangiate Filicineae.

Angiot^trmtt

Gymnosperma

Marsiliacem

Sahinimcea

Hepatica

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522 MOSSES AND FERNS

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524 MOSSES AND FERNS

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526 MOSSES AND FERNS

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2. Ueber Bau und Entwickelung der Riccien. Ibid.^ v., p. 364.

3. Entwickelung des Vorkeims der Polypodiaceen und Schizaeaceen. Sitzber. d.
Gesellschaft. naturf. Freund., Berlin, 1868.

4. Ueber Bau und Entwickelung des Famanlheridiums. Monatsber. d. Berlin.
Akad., 1869.

5. Beitrage zur Entwickelungsgeschichte der Farnkrauter. I. Osmunda regalis.
Pringsh. Jahrb. f. vriss. Bot., viii., 1872.

6. Entwickelung der Parkeriaceen dargestellt an Ceratopteris thalictroides. Nova
Acta der Kais. Leop. Carol, deutschen Akad. der Naturforschem, Bd. xxxvil, No. 4,

1875.

7. Treppengefasse in Famprothallien. Sitzber. d#»s bot. Vereins der Prov.

Brandenburg, 1874, p. 7'»

8. Durchwachsung an dem Wurzelhaare zweier Marchantiaceen. Sitzber. des
bot. Vereins der Prov. Brandenburg, Jahrgang 21, 1879, p. 2.

9. Entwickelung von Aspidium, filix-mas., I Theil. Berlin, 1895.

Kruch, O. — 1. Appunti sullo sviluppo degli organi sessuali e sulla fecondazione
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2. Istologia ed istogenia del fascio conduttore delle foglie di Isoetes. Malpighia,
An. iv., 1890, p. 56.

528 MOSSES AND FERNS

KiJHN, R. — I. Zur Entwickelungsgeschichte der Andreaeaceen. Schcnk und
Luerssen, Mitthl. aus dem Gesammtgebiete d. Botanik, vol. i.

2. Untersuchungen Uber die Anatomic der Marattiaceen und anderen GeTalss-
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3. Ueber den anatomischen Bau von Dansea. Flora, 1890, p. 147.

KiJNDiG, J. — Beitrage zur Entwickelungsgeschichte des Polypodiaceensporangiums.
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KUNZE, G.— Phylloglossum. Bot. Zeit., 1843.

Lachmann, p. — I. De I'accroissement terminate de la racine de Todea barbara.
Bui. de la Soc. botanique de Lyon, 1884, p. 42.

2. Sur I'origine des racines chez les foug^res. Bui. de la Soc. bot. de France, xxx.

3. Sur le syst^me lib^ro-ligneux des foug^res. Ibtd,^ p. 35, 1884.

4. Recherches anatomiques sur les Davallia. Bui. de la Soc. botanique de Lyon,
1886.

5. Sur la structure de la racine des Hym^nophyllac^es. Ibid.^ 1886.

6. Structure et croissance de la racine des foug^res, et Torigine des radicelles.
Bui. de la Soc. bot. de Lyon, 1887. •

7. Insertion des Racines. Ann. de la Soc bot. Lyon, 1889.

Leclerc du Sablon. — I. Sur le sporogone des Hepatiques et le role des
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2. Sur la d^eloppement du sporogone de FruUania dilatata. Bui. de la Soc. bot.
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3. Recherches sur la d^veloppement du sporogone des Hepatiques. Ann. des ScL
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4. Recherches sur le dissemination des spores chez les cryptogames vasculaires.
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5. Sur les anth^rozoides du Cheilanthes hirta. Bui. de la Soc bot. de France,
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6. Reviviscence de Selaginella lepidophylla. Ibid,

7. Sur Tendoderme de la tige des Selaginelles. Journal de Botanique, 1889,
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8. Recherches anatomiques sur la formation de la tige des fougeres. Annalcs des
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BIBLIOGRAPHY 529

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2 M

S30 MOSSES AND FERNS

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532 AfOSSES AND FERNS

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534 MOSSES AND FERNS

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INDEX

AcROCARPiE (Bryineae), 209
Adiantum, 355, 377

emarginatum, 329; apex of stem, 322 ;
stomata, 327. Figs. 162, 164,
165
pedatum, 325
Algae, I, 2, 508, 512, 515; zoospores,

9
green, 14, 82, 150, 509
Alsophila, 304, 373
contain inans, 373
Amblystegium, 183, 184, 185, 186
riparium, var. fluitans, 182 ; branches,
185 ; leaf, 183. Figs. 86, 87
Anabcena azollse, 389, 396
Andreaea. 153, 157, 172, 175, 176, 177,
1.78, 188, 192, 194, 201, 210,
216, 217 ; growth of stem and
leaves, 173; protonema, 174-;
pseudopodium, 172 ; sexual organs,
175; sporogonium, 176; spores,

174
crassinerva. Fig. 83.
petrophila, 173. Figs. 82, 83
rupestris, 173
Andreseaceae, 152, 157, 158, 172
Aneimia, 371, 372 ; stomata, 327

hirta, 371
Anelaterea, 95

Aneura, 9, 14, 15, 16, 71, 82, 83, 92,
103, 108, 115, 125, 149, 150, 255,
509, 510; embryo, 87; gemmae,

2,83
multifida, 82, 93; gemmae, 9, 12.

Fig. 36
'palmata, 89
pinguis, 89. Fig. 36
pinnatifida, 84 ; antheridium, 85 ;

archegonium, 86. Figs. 34, 35,

Angiopteris, 252, 255, 257, 265, 266,

268, 269, 270, 271, 272, 273, 274

299, 326, 332, 353, 357
evecta, 254, 271, 273 ; anatomy of

leaf, 269-271 ; germination, 255 ;

prothalliura, 257 ; sporangia, 272.

Figs. 130, 142, 143
Angiopterideae, 273, 274
Angiosperms, 280, 301, 517, 518, 519
Anisogonium Seramporense, 331
Annulariese, 459
Anthoceros, 14, 19, 52, 114, 116, 141,

143, 148, 156, 170, 178,202, 218,

296, 298, 351, 501, 505, 509, 510,
511, 513, 514, 515, 516; apical
growth, 119; chloroplasts, 120;
elaters, 134; embryo, 127; game-
tophyte, 117; mucilage-clefts, 119;
spores, development of, 1 33 ; sporo-
gonium, dehiscence, 136; stomata,

135

laevis, 117, 135, 136, 257, 512; an-
theridium, 122; archegonium, 125.
Figs. 60, 61, 62, 64, 65

fusiformis, 117, 119, 122, 126, 134,
136, 140, 429, 432, 465, 512?
apical growth, 119; germination,
1 36 ; infection with nostoc, 1 38.
Figs. 55, 56, 57, 58, 59, 63, 66,

67, 74
punctatus, 117
Vincentianos, 123
Anthoceroteae, 10, 14, 15, 19, 21, 22,
107, 114, 150, 216, 219, 261, 296,

297, 298, 505, 508, 509, 510, 511,
512; antheridium, 10, 16, 115;
archegonium, 10 ; archesporium,
116; chloroplasts, 115; mucilage-
slits, 15, 115 ; sexual organs, 115 ;
sporogonium, 115, 116

536

MOSSES AND FERNS

Apogamy, 221, 305, 369

Apospory, 221, 306, 369

Archegoniatae, 1 , 8 ; alternation of
generations, 2 ; antheridium, I ;
archegonium, i ; archesporium, 5 ;
fertilisation, 2 ; gametophore, 2 ;
gametophyte, 2, 3, 4, 5 ; inter-
relationships, 508 ; protonema, 2 ;
spores, 4, 5 ; sporophyte, 3, 4, 5

Arch^onium, 1

Archespermce (see also Gjrmnosperm,

I, 7) /

Archidium, 153, 158, 177, 478, 205,
217; sporogonium, 178
Ravenelii. Fig. 84
Aspidium, 377

filix-mas, 310 -t.

filix-mas var. cristatum, apogamy, 305

filix-mas var. falcatum, apogamy,

305
spinulosum. Fig. 194
^"Asplenium, 377
bulbiferum, 306
filix-fcemina, 310, 377
filix-foemina var. clarissimum, apo-

spory* 306
nidus, 376
Asterophyllite«, 459
Astroporae, 58
Ath5rrium (see Asplenium)
Atrichum, 156

undulatum, 153. Figs. 91, 106
— -Azolla, 7, 378, 380, 381, 382, 384, 386,
388, 389, 390, 392, 394, 395» 396,
398, 409, 418. 420, 421, 5'7
Caroliniana, 384, 386, 392
filiculoides, 382, 386, 392, 394 ;
antheridium, 381 ; archegonium,
383, 385; cotyledon, 387, 389;
embryo, 386; germination of macro-
spore, 382 ; of microspores, 381 ;
leaves, 392; macrosporangium, 396;
massulne, microsporangium, 398 ;
primary root, 388 ; second root,
389 ; sporocarp, 394 ; stem apex,
390. Figs. 196, 197, 198, 199,
200, 201, 202, 204, 205
Nilotica, 394

Blasia, 9, 12, 14, 71, 94, 95 ; gemma,
73, 94, 150; leaves, 14
pusilla. Fig. 38
Boschia, 42, 68 ; sporogonium, 58
Botrychium, 221, 231, 240, 252, 253,
254, 265, 271, 272, 292, 296,
299, 338, 351, 353, 355, 356, 357,
372, 419, 451, 465
lunaria, 223, 225, 248, 250 ; gameto-

phyte, 222 ; root of young plant,

227. Fig. 122
B. rutaefolium, 252

simplex, 240, 243, 248, 250. Fig.

122
tematum, 243, 247, 248, 249. Fig.

122
Virginianum, 227, 228, 240, 296, 298,

305, 357 ; anatomy of stem apex,

242 ; cambium, 245 ; germination,

224 ; growth of stem, 243 ; leaf,

240 ; root, 247 ; sieve-tubes, 247 ;

sporangia, 250 ; vascular bundles,

243, 246, 249. Figs, no, 123.

124, 125, 126, 127, 128, 129
Bryacese, 152, 157, 510
Bryineje, 158, 180, 208, 302, 498, 511 ;

apical growth, 182; buds, 181;

classification, 205 ; germination,

180; protonema, 180
Bryophyte, Bryophyta (see also Mus-

cineae), 3, 4, 8, 508, 5^3, 515
Buj^baumia, 8, 152, 154, 155, 158, 210,

215, 217. Fig. 106
Buxbaumiaceas, 215

Calamarie^ 459, 460

Calamites, 459

Gilamitece, 459

Calamostachys, 459, 516

Calobryum, 12, 71, 95

Camptosaurus rhizophyllus, 306

Casuarina, 518

Cephalozia bicuspldata (see Jungermannia

bicuspidata)
Ceratopteris, 375, 421
Chara^ 168
Characea;, I, 80, 508
Chiloscyphus, 108

combinatus. Fig. 54
Cibotium, 304, 328, 373

Chamissoi, 374

Menziesii, 373. Fig. 193
Cleistocarpae (Bryineae), 205, 207
Clevea, development of carpocephalum,

55. Fig. 18
Climacium, 155, 186

Americanum. Fig. 75
Codonieas, 95

Coleochaete, 14, 115, 505, 508, 509
Cololejeunea Goebelii, 112. Fig. 52
Confen-aceoe, 505
Conifers, 505, 506, 517, 519
Conocephalus, 14, 20, 22, 42, 139;
air ghambers, 42, 43 ; germinaiion,

47
conicus, mucilage-ducts, 44. Fig. i

INDEX

537

Corsinia, 42, 47^68 ; sporogoiuBm, 58.

Fig. 20 ^
marchantioides. Fig. 2(>
Corsinieae, 21, 47, 67, 69
Cronbia paradoxa, 41
Cupulifene, 252
Cyathea, 304, 373
medullaris, 373
Cyatheaceae, 304, 307, 308, 372, 374,

375, 419, 421 ; embryo, 373; pro-

thallium, 373 ; sexual organs, 373 ;

sporangium, 373
Cyathodium, 68
Cycads, 517, 518
Cystopteris bulbifera, 221, 306. Fig.

195

DaN;€A, 254, 271, 274

Danaeaceae, 274
Darlingtonia, 11 1

Dendroceros, 114, 135, 138, 144, 148,
313, 341, 512; elaters, 139;
gemmae, 139; germination, 139;
sexual organs, 1 39 ; thallus, 1 38
cichoraceus, 138, 139
Javanicus, 138, 139. Figs. 55, 74
Diatoms, 122
Dicksonia, 328

antarctica, 373
Dicotyledons, 245, 518
Dracaena, 292

Dumortiera, 22, 23, 42 ; structure of
thallus, 49
irrigua, 49
trichocephala, 49

ElaterE/E, 95

Ephemerum, 155, 180, 205, 207, 217;
sporogonium, 205

phascoides. Fig. 103
Epigonianthex, 113

Equisetum, 5, 226, 248, 249, 422, 425,
427, 461, 464, 465, 466, 478,
484, 496, 512, 514, 515; arche-
gonium, 429 ; assimilative tissue,
442 ; buds, 445 ; cotyledon, 434 ;
embryo, 432; epidermis, 444;
rhizome, 435 ; roots, 447 ; spores,
423 ; sporophyte, 435 ; stomata,
444

arvense, 422, 436, 439» 443» 446,
453» 456, 457. Fig. 226

giganteum, 422, 447

hiemale, 457

limosum, 443, 453, 457. Figs. 232,
242

maximum (see E. telmateia)i 457

E. palustre, 448. Fig. 226
pratense, 457
robustum, 457, 459
scirpoides, 432, 439, 446, 459- Fig-

242
sylvaticum, 447

telmateia, 422, 425, 427, 434, 436,
439, 441, 442, 443, 444, 446, 448,
453» 454, 457, 459 ; antheridium,
425, 426 ; archegonium, 429; cam-
bium, 457 ; embryo, 432 ; endo-
dermis, 443 ; epidermis, 444 ; ger-
mination, 423 ; lacunae, 434, 442 ;
leaves, 439, 457 ; prothallium, 424,
425 ; roots, 447, 450 ; sp>ermato-
zoids, 427 ; sporangia, 450 ; spores,
423, 453, 456 ; stem apex, 432 ;
stomata, 444 ; tannin cells, 442 ;
tubers, 436 ; v^tscular bundles, 442,
449. Figs. 218, 219, 220, 221,
222, 223, 224, 225, 227, 228, 229,
230, 231, 232, 233, 234, 235, 236,
237, 238, 239, 240, 241
variegatum, 450, 457

Equisetacese, 6, 459 ; E. cryptopora,
457 ; E. phanopora, 457

Equisetinex, 220, 422, 515, 516, 519;
affinities, 460 ; classification, 457 ;
fossil, 459

Equisetites, 459

Eurynchium praelongum, 152

Eusporangiatae (Filicineae), 222, 298,
304, 307, 321, 338, 419, 421, 426,
430, 453, 460, 464, 466, 516, 518,
519; affinities of, 295

Fegatella (see Conocephalus)

Ferns (see also Filicineae), 13, 220, 461
Tree-ferns, 304, 328

Filices, 221, 307 ; leaf, structure of,
325 ; roots, 328 ; sporangia, 331 ;
trichomes, 428

Filicinece (see also Ferns), 220, 460, 515,
518, 519

Fimbriaria, 16, 19, 42, 48, 64, 70;
carpocephalum, 55 ; perianth, 64.
Fig. 14
Califomica, 24, 50, 55, 59, 258;
antheridium, 50, 51 ; breathing-
pores, 48, 57, 58 ; development of
the thallus, 47, 48 ; germination,
64, 65 ; spores and elaters, 63, 64.
Figs. I, 10. 13, 15, 19, 20, 24, 27

Fissidens, 153, 208

Fontinalis, 8, 152, 155, 186, 187, 192,
209; peristome, 210
antipyretica, apical growth, 182. Fig.
106

538

MOSSES AND FERNS

Fossombronia, 14, 71, 73, 94, 138, 150
longiseta. Figs. 37, 38

Frullania dilatata, embryo, 106, 107.
Fig. 50

Funaria, 184, 185, 209, 214
hygrometrica, 152, 157, 182, 209;
annulus, 201 ; antheridiutn, 188 ;
archegonium, 191 ; calyptr^, 205 ;
capsule, 198; embryo, 194; epi-
dermis, '201 ; lacunae, 198 ; para-
physes, 191, 193 ; peristome, 201,
204; rhixoids, 186; seta, 198;
spermatozoids, 191 ; sporogonium,
I97» 198 ; stomala, 202. Figs.
85, 88, 89, 90, 91, 92, 93, 94, 95»
96, 97, 98, 99» >oo, loi, 102

Gleichenia, 357, 358, 359, 364, 365,
366, 369, 371 ; embryo, 359 ; pro-
thallium, 358 ; sexual organs, 358 ;
sporangia, 359 ; structure of stem,

359
dichotoma, 357, 358. Fig. 185

Gleicheniaceae, 307, 357, 374, 419, 420,
421

Gnetaceae, 517, 518

Gold-back fern (see Gymnogramme tri-
angularis)

Grimaldia, 55, 59, 64

Gymnogramme leptophylla, 305
triangularis, 328

Gymnosperras, i, 300, 469, 505, 507,

517, 518, 519
Gymnostomum, 209

Haplomitrium, 12, 71, 95, 96, 150 j
Haplomitriese, 73, 95 '

Helminthostachys, 252, 299, 338, 356, |

357, 419 I

Zeylanica, 252. Fig. 122
Hemiphlebium, 366, 367

Hookeri, 367
Hepaticae (see also Liverwoits), 8, 9, 13,

297, 341, 508, 510, 512, 519;

calyptra, 12 ; classification, 21 ;

dehiscence of sporogonium, 19 ;

elaters, 12; germination, germ-tube,

20 ; interrelationships of, 149 ;

sp>ore5, 19, 20
Heterospory, 10
Hippochaete, 457
Hydropterides, 221, 304, 307, 378, 384,

419, 420
Hymenophyllum, 305, 353, 360, 362,

363, 366, 367, 368, 373, 375, 512 ;

amheridium, 363 ; archegonium,
364 ; gemmw, 362, 363 ; leaf, 366 ; |

prothallium, 360 ; root, 367. Figs.
187, 188, 189

H. demissum, 367
dilatatum, 366
recurvum. Fig. 190

Hymenophyllaceae, 304, 305, 307, 360,
367, 371, 372, 375, 379* 382, 392,
420, 421 ; embryo, 365 ; gamcto-
phyte, 360; leaf, 2lb6 ; sporaogiom,
367 ; sexual organs, 363 ; stem,
366 ; trichomes, 367

Hymenophyllites, 419

Hymenostomum, 209

Hypenantron (see Fimbriaria)

Hypnum, 153

ISOETES, 274, 275, 292, 300, 302, 383,

385, 484, 485, 487, 49i» 506, 507,
516, 517, 518, 519; embryo, 283;
gametophyte, 276 ; leaf, 292 ; root,
293j^sporangium, 293; secondary
growth of stem, 291 ; stem apex,
28V1 vascular bundles, 286, 288,
290, 291, 292, 293

echinospora var. Braunii ; anther-
idium, 277 ; archegonium, 280 :
cotyledon, 284, 286 ; embryo, 283 ;
foot of embryo, 285, 288 ; germina-
tion, 278 ; macrospore, 278 ; prim-
ary root, 284 ; spepnatozoids, 278.
Figs. 145, 146, 147, 148, 149, 150,
151, 152, 153, 154

hystrix, 276

lacustris, 276, 283, 291, 292, 293,
294, 295 ; budding of sporophylls,
295 ; development of roots, 293.

Fig. 155
Malinvemiana, 276. Fig. 145
setacea, 276. Fig 145
Isoetacew, 221, 254, 274

JUBULOiDEi€, 113

Jungermannia, 109
bicuspidata, 103, 107

Jungermanniacepe, 12, 14, 15, 16, 19,
21, 47, 64, 71, 73, 114, 136, 147.
'5^, 509 ; antheridium, 72 ; arche-
gonium, 1 5 ; classification, 96 ;
dehiscence of sporogonium, 73 ;
gemmae, 73» "2
Acrogynoe, 73, 94, 96 ; ampbigastria,
96 ; branching, 96, 98 ; cUssiSca-
tion, 113; lea\'es, 1 1 1
AnacTogynae, 73, 74, 82, 94, 149,
508, 510, 512; apical growth,
89 ; calyptra, 93 ; classihcation,
95 ; embryo, 87 ; sexual organs,
84,89

INDEX

539

Kaulfussia, 254, 255, 273, 274

aesculifolia, 274
Kaulfussieae, 274
Kinoplasm, 17

Laccopteris, 375

Lejeunia, 108, no

metzgeriopsis, no, 112. Fig. 52
serpyllifolia. Fig. 51

Lepidodendron, 295, 300, 485, 507

Lepidodendreae, 506, 507

Lepidostrobus, 507

Leptopteris, 353

Leptosporangiatae (Filicinese), 221, 301,
302, 325. 328, 331. 338, 354, Z^l.
4i7> 516, 519; affinities of, 419;
^uds, 331 ; classification, 306 ; em-
bryo, 303 ; fossil L., 419 ; L.
heterosporeae, 378 ; L. homo-
sporeae, 302, 388; non-sexual re-
production, 304 ; sporangia, 304,
33 1 ; trichomes, 328

Leptothecese, 95

Leucobr)'um, 208. Fig. 107

Liverworts (see also Hepaticae), 2, 6, 8,
I3» 297, 298, 505, 508, 509, 510,
511, 512, 516; apical growth, 1 5 ;
secreting cells, 14 ; sexual organs,

15
Lophocolea, 108
Loxsoma, 360

Cunninghamii, 360
Lunularia, 44, 58, 64 ; gemmae, 24, 44,

45
Lycopodium, 300, 461, 463, 464, 466,

469, 470. 473» 474, 475, 47^, 478,
479, 480, 482, 485, 491, 493, 495,
496, 499, 500, 501, 502, 503, 504,
505, 506, 507, 513, 514, 515;
embryo, 467 ; gametophyte, 464 ;
gemmae, 473, 475 ; leaf, 468,
47 *, 473; protocorro, 468; root,
469, 474 ; root-hairs, 474 ; sexual
organs, 465 ; spermatozoids, 466 ;
sporophyte, 469; sporangium, 476;
stem, 470, 473 ; vascular bundles,
469, 471, 472, 473, 475

aloifolium, 473

alpijum, 473, 475

annotinum, 464, 465, 504 ; pro-
thallium, 465

cernuum, 464, 465, 467, 469, 470,
504, 512 ; embryo, 467 ; pro-
thallium, 464. Fig. 244

clavatum, 469, 475, 478, 484. Figs.

243, 249
complanatum, 469
dendroideum. Fjg. 243

L. inundatum, 461, 463, 464, 465, 467,

469, 474, 476 ; germination, 464 ;

mucilage ducts, 476 ; prothallium,

465 ; root, 469
lucidulum, 470, 475 ; gemmae, 475.

Figs. 246, 248
phlegmaria, 465, 466, 467, 469, 470,

504 ; embryo, 467 ; paraphyses,

467 ; prothallium, 465 ; sexual

organs, 466, 467. Figs. 244, 245
reflexum, 473
selago, 470, 473, 474, 475, 476, 478,

502; gemmae, 475; root, 474;

sporangium, 476 ; stem apex, 470.

Figs. 247, 248, 249
taxi folium, 473
verticillatum, 473
Lycopodineae, 220, 274, 300, 461, 485,

506, 514, 515, 519; affinities of,

504 ; classification, 463 ; fossil L.,

506
Lycopodiaceae, 463, 504, 515, 519
Lycopodites, 506
Lygodium, 370, 371, 372
Japonicum. Fig. 192

Marattia, 226, 255, 265, 268, 270,
271, 272, 273, 274, 278, 280, 282,
284, 297, 298, 303, 309, 313, 318,
319, 320, 321, 341, 345, 351, 427,
428, 466
Douglasii, 257, 259, 266 ; anther-
idium, 259 ; archegonium, 260 ;
cotyledon, 266 ; embryo, 262 ;
fertilisation, 261 ; foot of embryo,
265 ; germination, 255 ; primary
root, 265 ; prothallium, 255 ; second
root, 268 ; spermatozoids, 259 ;
stem apex, 264 ; tannin cells, 266 ;
vascular bundles, 266, 267. Figs.
131, 132, 133, "34, >35, 136,

m^ 138, 139, >40, 141, 142

Marattiaceae, 6, 219, 221, 222, 254, 263,
280, 296, 298, 299, 304, 310, 340,
341, 342, 344, 353, 516; classifi.
cation of, 273 ; fossil M., 274 ;
sporangium, 271

Marattieae, 273, 274

Marchantia, 12, 14, 16, 44, 49, 51,
59, 64, 67, 68, 69, 70, 73, 95,
113, 284; antheridial receptacle,
52 ; carpocephalum, 57 j egg, 54 ;
gemmae, 45 ; pores, 58
polymorpha, 24 ; antheridium, 50 ;
carpocephalum, 57; gemmae, 45, 46 ;
sporogonium, 64. Figs, fi, 12
geminata, 52

540

MOSSES AND FERNS

Marchantiaceae, 2, 8, 9, 14, 15, 19, 21, '
22, 68, 71, 72, 73, 76, 79, 80, 82, '
88, 90, 93, 114, 117, 149, 150,
I5i» 509* branching, 46; diagnosis
of M., 21 ; growth of thallus, 24 ;
oil bodies, 44 ; resume of M., 69 ;
rbizoids, 22 ; sexual receptacles,
47 ; sporophyte, 24

Marchantiea?, 22, 42, 63, 67 ; air
chambers, 22, 42, 48 ; branching,
' 46 ; classification, 67 ; elaters, 22,
47 ; pores, 22, 42 ; rbizoids, 42 ;
spores, 47 ; sporogonium, 22, 47 ;
ventral lamellae, 48

Marsilia, 5, 398, 399. 401, 402, 403,

404, 405, 406, 407, 409, 410, 412,
413, 414, 416, 418, 419, 421, 487 ;
cotyledon, 407 ; fool, 409 ; leaf,
413; root, 409, 413; stem, 410,
412 ; sporocarp, 399 ; vascular
bundles, 413, 414

-^gyptiaca, 399

Drummondii, 413

hirsuta, 414

polycarpa, 412

quadrifolia, 413

salvatrix, 413

vestita, 221, 400, 401, 402, 403, 404,

405, 410, 413, 414; antheridium,
401 ; archegonium, 404, 405 ; em-
bryo, 407 ; germination, 401, 404 ;
macrospore, 403 ; microspore, 400 ;
spermatozoids, 402 ; stem apex,
412. Figs. 206, 207, 208, 210,
212, 215

Marsiliaceae, 7, 221, 307, 378, 398, 403,
405, 420, 421, 491, 516, 517;
fertilisation, 405 ; sporocarp, de-
velopment of, 414 *

Mastigobryum, branching of, 1 1 2. Fig.

Matonia, 374, 375 4

pectinata, 374 •
sarmentosa, 374
Metzgeria, 14, 71, 82, 84, 108, no,
"5» 309» 34 1 » 509 ; apical growth,
82 ; branching, 83 ; embryo, 87,
88 ; sexual organs, 84 ; thallus,
82
furcata, 84, 87
pubescens. Fig. 33
Metzgeriaceae, 73
Metzgerieae, 95
Mnium) 153, 360
Mohria, 371, 372
Monocotyledons, 276, 285, 292, 300,

442,. 518
Morkia (see Pallavicinia)

Mosses (see also Musci), 2, 9, 11, 12,
13, 152, 302, 360. 509, 510, 511 ;
antheridium, 156 ; arch^ooiuin,
156 ; dehiscence of capsule, 157 ;
gemmae, 154; leaf, 154; non-sexual
reproduction, 154; protonema, 153 ;
rbizoids, 1 54; sporogonium, 157;
stem, 154; stomata, 157

Musci (see also Mosses), 8, 152, 519;
affinities of, 216; calyptra, 13;
^ ' columella, 13 ; operculum, 13

Muscineae (see also Bryoph)rta), 8, 508,
509, 512 ; antheridium, 10 ; aiche*
gonium, 10; asexual reproduction,
9 ; classification, 12 ; dehiscence of
sexual organs, 1 1 ; fossil M., 215 ;
gametophore, 9 ; origin of sexual
organs, 1 1 ; paraphyscs, 1 1 ; peri-
chaetium, 1 1 ; protonema, 9 ; sporo-
phyte, 12

NosTOC, 95, 115, 117, 119. 122, 138,

139
Notothylas, 19, 114, 115, 116, 140, 150,
151, 170, 171, 178, 217; arche-
gonium, 140 ; antheridium, 140 ;
embryo, 141 ; thallus, 140

melanospora, 147

orbicularis, 116, 122, 140, 142, 147.

Figs. 55, 68, 69, 70, 7i» 72, 73.

74
valvata (see N. orbicularis)

CEdogonium, 515

Onoclea, 308, 310, 314, 319, 335, 340,
341, 345, 348, 349» 35 "» ^77
sensibilis, 308

slruthiopteris, 308, 321, 323, 324, 325,
326, 328, 334, 335 ; air chambers
of rhizome, 323; antheridium, 310;
apical growth of prothallium, 313 ;
archegonium, 313 ; cotyledon, 317,
320 ; . embryo, 315 ; fertilisation,
315; foot of embr>*o, 319; germina-
tion of spores, 308 ; leaf, 320, 321,
325 ; prothallium, 310, 313 ; root,
319, 321 ; sclerenchyma, 323 ;
spermatozoids, 312, 313; spores,
308, 335 ; stem, 318,* 321 ;
stomata, 326 ; vascular bundles,
319, 320, 321, 322, 323, 324.
Figs. 156, 157, 158, 159, 160,
161, 162, 163. 194

Ophioderma (see Ophioglossum pendu-
lum)

Ophioglossum, 4, 220, 235, 240, 242,
243, 244, 247^248, 250, 251, 252,

INDEX

541

265, 266, 269, 280, 292, 295. 296,
297, 298, 300, 415. 460, 461, 51 1»
513. 514, 515. 5«6; adventive
buds, 239
O. Lusitanicum,*230

palmatum, 240

pedunculosum, embryo, 22% ; gameto-
phyte, 222 ; sexual organs, 222.
Fig. 108

pendulum, 224, 228, 235, 236, 239 ;
anatomy of leaf, 233 ; germination,
224 ; root, 235, 236 ; sporangio-
phore, 233 ; sporangia, 236 ; stem
apex, 230 ; vascular bundles, 232,
234. Figs. 109, 112, 114, 115,
116, 117, 118, 119, 120, 121

vulgatum, 231, 232, 235, 236, 237,
239, 293. Fig. 113
Ophioglossaceae, 218, 221, 222, 259,
261, 265, 271, 296, 299, 305, 419,
466, 516 ; symbiosis of, 252
Osdllaria, 122

Osmunda, 5, 226, 273, 299, 331, 335,
338, 340, 353, 355, 356, 358, 359,
363, 364, 365, 366, 372, 373, 406,
426,427; antheridium, 343; arche-
gonium, 345 ; budding of pro-
thallium, 342 ; cotyledon, 349, 350 ;
embryo, 348, 351 ; fertilisation,
347 ; foot of embryo, 351 ; leaf,
353; root, 351, 354; spermato-
zoids, 345

cinnamomea, 340, 341, 343, 347, 353,
354, 355, 5"2; hairs, 353; root,
354 ; sporophylls, 353. Figs. 170,
171, 173, 175, 176, 177, 178, 182,
184

Claytoniana, 340, 341, 343, 347, 353,
354, 355- figs. 169, 171, 172,
173, 174, 176, 178, 179, 180, 181

regalis, 338, 340, 342, 347, 352, 354;
apical growth, 352; vascular bundles
of stem, 352. Figs. 181, 183
Osmundaceae, 304, 307, 338, 342, 419,
420, 421, 516; germination, 339;
prothallium, 341 ; sporangium, 356 ;
spores, 338
Ostrich Fern, 308
Oxymitra (see Tessalina)

Pallavicinia, 14, 15, 89, 92, 93;
perianth, 93, 119
cylindrica, apical cell, 89. Figs. 38,

decipiens, spore division, 93
Pellia, 9, 20, 72, 102, i<3^ 139, 147,
150, I74i 510; antheridium, 90;

embryo, 92 ; germination, 94 ;
spermatozoids, 17, 92
P. epiphylla, 94, 139, 3^3, 34 1 J apical
cell, 89 ; arch^onium, 89 ; growth
of seta, 93 ; spermatozoids, 1 7 ;
sporogonium, 92 ; spores, 94. Fig.

39
calycina, 89, 94

Phanerogams (see also Spermaphytes),
271

Phascum, 207, 20^

cuspidatum, 207. Fig. 103

Phascaceae, 153, 158, 180

Phoradendron, 480

Phylloglossum, 463, 478, 480, 504,
505, 5'3» 5»4, 515 J anatomy of
vegetative organs, 479 ; protocorm,
479 ; sporangium, 479 ; sporo-
phyte, 479
Drummondii, 463, 478. Fig. 249

Phylloglosseae, 480

Pilularia, 221, 401, 402, 403, 404, 405,

406, 407. 408, 409, 410, 412, 413,
414, 418, 419, 421 ; embryo, 407 ;
fertilisation, 406 ; sporophyte, 410

Americana, 221, 413, 414, 416, 418 ;
development of sporocarp, 414 ;
sporangium, 417. Figs. 214, 216,
217

globulifera, 404, 405, 406, 413, 416,
418 ; antheridium, 402 ; cotyledon,
406 ; macrospore and female pro-
thallium, 403 ; spermatozoids, 403 ;
stem apex, 408, 410. Figs. 209,

2IlJ>I3

Plagiochasma, female receptacle, 55
Platycerium, 376
alcicome, 376
Wallichii, 331
Platyzoma, 357

microphyllum, 357
Pleuridium, 207, 208

subulatum. -Figs. 103, 104
Pleurocarpae (Bryineae), 208
Polypodium, 332, 376, 420

falcatum, 329, 336 ; development of
sporangium, 332-336. Figs. 166,
167, 168
lingua, 327
Polypodiaceae, 302, 307, 308, 310, 315,
321. 323, 324, 33«, 336, 340, 341.
344, 345, 349, 352, 353, 355, 358,
366, 370, 371. 372, 373, 375, 402,

407, 413, 4x7, 419, 420, 421,
516; embryo, 315; gametophyte,
308,309,310; leaf, 317, 325; para-
physes, 337 ; root, 319, 328, 331 ;
sexual organs, 310, 311, 312, 313,

542

MOSSES AND FERNS

314, 315 ; sporangium, 332 ; stem,
318, 321 ; stomata, 326; vascular
bundles, 320, 323, 326, 330

Polystichum angulare var. pulcherrimum,
apospory of, 306

Polytrichum, 154, 156, 218 ; leaf, 212 ;
stem, 212; sporogonium, 214
commune, 209. Figs. 106, 107
formosum, 209
juniperinum, 213

Polytrichaceae, 155, 157, 209, 210, 212 ;
male flowfer, 214

Porella, 96, 99, 100, 102, 103, 107,
108, 168 ; amphigastria, anther-
idium, 98, 99, 100 ; apical growth,

97 ; archegonium, 102 ; branches,

98 ; embryo, 103 ; leaves, 96 ;
spermatozoids, 100 ; sporogonium,
104 ; spores and elaters, 104 ^

Bolanderi, 96. Figs. 41, 42, 44, 45,

46, 47, 48, 49
platyphylla, 96
Preissia, 14, 59, 68; sclerenchyma, 14,

44
commutata, 44 ; archegonium, 52

Protocephalozia, 73
ephemeroides, 109

Psilophyton, 506

Psilotites, 506

Psilotum, 463, 480, 482, 484 ; gemmre,
480 ; sporangium, 484 ; spocophyte,
480
triquetrum, 480. . Figs. 250, 251

Psilotacese, 463, 480, 504, 506, 515,
519; affinities, 504; fossil P., 506;
sporophyte, 480 ; sporangium, 483

Pteridophytes, 3, 4, 6, 218, 297, 298,
299, ZOO, 422, 460, 467, 474» 479»
485. 505. 506, 511, 512, 513,
514, 516, 517, 518, 519; embryo,
3; heterospory, 7, 516; pro-
thallium, 4, 7 ; sexual organs,
219; sporangium, 4, 220; sporo-
phyte, 3, 4 ; vascular bundles, 4

Pteris aquilina, 302, 306, 376 ; apo-
spory,'306. Fig. 163
Cretica, 305, 329

Ptilidioideae, 113

Radula, 104, 107, 174; germination,
108

complanata. Figs. 50, 51
Reboulia, 42 ; carpocephalum, 55

hemisphfcrica. Fig. 18
Rhizocarpese (see Hydropterides)
Rh)mcos(egium murale, 152
Riccardia (see Aneura)
Riccia, 12, 14, 15, 16, 22, 40, 41, 46,

47» 48, 50. 52, 67, 69, 75, 79* So*
ii7> I49» 508, 509, 511 ; adven-
tive buds, 28 ; air chambers, 27 ;
antheridium, 32 ; archegonium, 29,
30 ; archesporium, 35 ; branching,
28 ; calyptra, 37 ; embryo, 34 ;
epidermis, 27 ; growth of thallns,
25 ; root hairs, 28 ; spermatozoids,
33 ; spore division, 35, 36 ; sporo-
gonium, 18 ; tissues, 29 ; ventral
lamellae, 27
R. Bischoffii, 27, 30, 3I

crystallina, 28

fluitans, 25, 28, 40

glauca, 25, 27, 29, 32, 37. Figs,
I, 2, 3» 4, 5. 6

hirta, 24, 29, 30, 65 ; development of
spores, 36 ; germination, 37. Figs.
4, 5. 6» 7. 8, 9

natans (see Ricciocarpus)
Ricciacese, 18, 19, 22, 25, 42, 68, 74 :
classification, 40; diagnosis, 21 ;
sexual organs, 29
Ricciocarpus, 8, 40, 43, .48, 68 ; struc-
ture of thallus, 40

natans, 40 ; ventral scales, 27
Riella, 8, 12, 14, 71, 72, 80, 82, 95

lielicophylht^ 8i.v Fig. ^2

Parisii, 8j ^

Riellcae, 72

Salvinia; 331, 378, 380, 382, 384,
385, 386, 3^, 390, 392, 393. J94t
395» 396, 398,419. 420, 421
natans, antheridium, 380 ; arche-
gonium, 386 ; branching of sporo-
phyte, 394 ; embryo, 388 ; leaves,
393 ; microspore, 380 ; prothallium,
380, 385 ; spermatozoids, 380 ;
sporangia, 394, 398; sporocaip,
379» 398 ; sporophyte, 390 ; stem
apex, 390 ; vascular bundles, 394.
Figs. 196, 203

Salviniaceae, 221, 304, 307, 378, 380.
420, 421, 516, 517

Scapanioidex, 113

Schistostega, 208

Schizaea, 371, 372
pusilla, 370

Schizieaceae, 307, 308, 370, 420 ; game-
tophyte, 370 ; leaf, 371 ; root, 372 ;
sexual organs, 371 ; sporangium,
372; stem, 371 ; trichomes, 371 ;
vascular bundles, 371

Scolopendrium, 376 V* Ht

Selaginella, f, 11$, 300. 461. 403, ,485,
^86, 487, 491, 495» 5«>» 503» S^S^

INDEX

543

.506, 507, 512, 517; antheridium,
4S6, 487 ; archegonium, 490, 491
branching, 494, 496 ; chloroplasts,
500 ; cotyledons, 492, 494 ; em
biyo, 491 ; female prothallium, 487
leaves, 495 ; macrospore, macro
sporangium, 7 ; male prothallium,
486; microsporangium, 501 ; rhizo
phore, 495; rodjs, 493, 500
spermatozoids, 487 ; sporophyte,
495 ; stem apex, 496 ; vascular
bundles, 498, 500
S. apus, 493

arborescens, 496

Kraussiana, 486, 493, 494, 495, 496,
498, 499, 500, 502 ; anatomy of
stem, 496, 497, 498, 499 ; develop-
ment of female prothallium, 487,
488, 489, 490, 491 ; root, 500 ;
sporophyte, 495 ; sporangia, 501 ;
vascular bundles, 498, 500. Figs.
253, 254, 255, 256, 258, 259,
260, 261, 262, 263, 264, 265,
266

laevigata, 499

lepidophylla, 485, 499

Martensii, 491, 493, 494, 496, 499,
500, 501, 503 ; embryo, 491, 492.
Figs. 257, 264

rupestris, 461, 485, 495

spinosa, 501

Wallichii, 496

Wildenowii, 500
Selaginelle», 463, 485, 504, 515, 519
Sigillarieoe, 507 *

Spermaphytes, 4, 154, 244, 295, 300,
460, 489, 505, 516, 517, 519;
embryo sac, 7 ; o\'ule, 7 ; seed, 7
Sphaerocarpus, 15, 16, 18, 72, 74, 81,
82, 89, 95, 141, 149; I5C^» 15^
511; antheridium, 79, So; apical
growth, 75 ; archegoniuni, 75, 76 ;
embryo, 76, 77, 78 ; germination,
80 ; spermatozoids, 80 ; sporo-
gonium and spores, 78 ; ventral
hairs, 75

Michelii (see S. terrestris)

terrestris, 74

terrestris var. Califomicus. Figs. 28,

29» 30» 3>
Sphagnum, 5, 152, 153, 154, 156, 158,
I75» 176, 177. 180, 182, i>3, 186,
189, 191, 192, 194, 201, 209,^0,
216, 217, 509, 511 ; amphithecJipn,
170; antheridium, 166; apical
growth, 160; archesporium, 171;
archegonium, 168; branching, 158,
165; embryo, 170; endothecium.

170; gametophore, 160; germina-
tion, 159 ; leaves, development of,
162 ; phyllotaxis, 159 ; protonema,
160; pseudopodium, 157, 172;
rhizoids, 159, 160; spermatozoids,
168 ; spores, 17 1 ; sporogonium,
1 70 ; stem, tissues of, 164 ; vaginula,
172

S. acutifolium, 170. Figs. 79, 80, 81
cynjl^foUum, 165. Figs. 77, 78, 79;^

Sphagnace», 147, 153, 157, 158, \^^\
217, 509

Spirogyra, 64, 414

Splachnum, 212, 218
ampullaceuro. Fig. 106

Steetzia (see Pallavicinia)

Stegocarpae (Bryineoe), 208

Stephaninoideae, 113

Stigeoclonium, 115

Stigraaria, 507

Stromatopteris, 331

Struthiopteris Germanica (see Onoclea
^truthiopteris)

Targionia, 42, 46, 48, 52, 53, 57, 59,
67, 68, 93, 117
hypophylla, 24; antheridium, 51;
archegonium, 52, 53, 54; arche-
sporium, 60 ; ^%, 54 ; embryo,
59, 60 ; elaters, 64 ; germination,
64 ; sporogonium, 61. Figs. I, 16,
17, 21, 22, 25, 26
^Michelii (see T. hypophylla)
Targionieae, 67, 68, 69
Tessalina, 42, 68, 69

pyramidata, structure of thallus, 41
Tetraphis, 10, 153, 181, 209, 216, 217
pellucida, 1 54, 209 ; gemmae, 209
Fig. 105
Tetraphidece, 209
Thallocarpus, 95
Thuidium, 153, 186
Tmesipteris, 463, 480, 482, 483, 484 ;
sporangiophore, 483, 484
Tannensb. Fig. 252
Todea, 338, 341, 353, 355, 356
Africana, apogamy of, 305
barhara, 353, 354 ; root apex, 354
Treubia, 95, 96, 150

insignis, 94
Trichomanes, 303, 342, 360, 361, 362,
363* 365» 366, 367, 368, 369, 395»
420, 512; antheridium, 363;
archegoniophore, archegonium, 365 ;
germination, 360 ; indusium, 368 ;
leaf, 366 ; placenta, 368 ; pro-
thallium, 361 ; root, 367 ; sporan-
gium, 367

.#^

544

MOSSES AND FERNS

T. alatum, 361, 369 ; apogamy and apo-
spory, 369

brachypus, 367

cyrtotheca, 369 ; development of spor-
angium, 368, 369. Figs. 190, 191

Draytonianum. Fig. 186

pyxidiferum, 361, 367

radicans, 366, 367

reniforme, 366
Trigonantheae, 113
Trochopteris elegans, 370

Vascular cryptogams (see Pterido-

phytes)
Viscum, 480
Vittaria, 221, 375, 376

Walking Fern (see Camptosaurus)
Wcbera nutans, 152
Weisia, 152

Yucca, 292

THE END

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